Syntax concerns the way that words are arranged into larger units. That is, words are the basic units—the building blocks—of syntactic analysis. The largest unit that syntactic analysis usually considers is the sentence. For this reason, syntax is often equated with the study of sentence structure, even though the things we analyze may not always be complete sentences. Language, of course, rarely consists merely of isolated sentences. We string sentences together into larger units—paragraphs, essays, books. When we spend a great deal of time focused on sentence-level analysis, as we will in the following chapters, it’s easy to lose sight of the larger purposes of syntactic study. So before we plunge into the forest, it’s worth considering why we should spend so much effort on the task.
Some people—and I count myself among them—find that syntax has its own inherent fascination. I won’t hold it against you, however, if you’re not one of those people. There are still many good reasons to learn something about syntax. Writing in any sort of formal context—a college paper, a memo at work, or a newspaper article—requires some knowledge of syntax. To understand the conventional rules for sentence punctuation, for example, you must first understand clause and phrase structure. Beyond mere mechanics, a thorough understanding of syntax also gives you a way to take control of your own writing. When you understand how sentences are put together, you will be able to analyze your own writing and understand the structures that you have been using intuitively. You will also be able to see what other options are available to you, how it might otherwise be done. Those who write for a living or who help others with their written expression—teachers, editors, etc.—have an even greater need to know how to analyze syntax.
When we analyze a sentence, we take it apart to determine what function each unit in the sentence has. This process is known as parsing a sentence. You can probably do some basic parsing already, even if you have never heard of the term. For example, if you can identify the subject of a sentence, you have analyzed the sentence and identified the role of one important item in it. Congratulations, you have just parsed a sentence, although not completely.
Over the next ten chapters, we will develop a progressively more detailed account of English syntax. As we begin our study, you should be aware that syntax is an interrelated system. As a result, learning how to analyze it can be challenging because to understand one part you often need to know about something else. Occasionally we will have to introduce a term before defining it completely. In these cases, you may find it helpful to reread earlier sections after you understand the concept. We start with relatively general points and refine our account as we learn more about the various components of grammar. As our account grows more detailed, we will be able to analyze more and more complex sentences. From time to time, this added complexity will force us to refine our account when our first approximation turns out to be inadequate. Although it may seem more convenient to work from the beginning with a single “correct” system, that method is actually impractical. If we did so, we would drown in detail before understanding the basics.
The chapters that follow do contain many details, but they will not be exhaustive. No book can give a complete account of something as flexible and multifaceted as a human language. Even more important than all the terminology and diagrams that we use to describe syntactic structure are the basic principles that will let us think through problems on our own. When we turn to examine real-world language, as opposed to the deliberately controlled sentences of grammar books, we must understand the principles that underlie grammatical structure and apply our knowledge.
If we look at the components of a sentence, we can say that a sentence consists of a string of words. But if we look more closely, it’s easy to see that the words aren’t all equal. Instead, they occur in groups. Consider the famous opening sentence of Leo Tolstoy’s Anna Karenina:
(1) All happy families resemble one another, but each unhappy family is unhappy in its own way.
It’s not very helpful to think of the individual words in isolation. What, for example, is the relationship between each and resemble? In fact, they don’t have a direct relationship. They are more closely related to other words in the sentence than they are to each other. We can appreciate some of this structure by dividing the sentence into some of its component parts.
First, we can see that this sentence breaks down into two halves:
| a: | All happy families resemble one another, |
| b: | but each unhappy family is unhappy in its own way. |
And in each of these parts, we can identify smaller units, for example[1]
| a: | [All happy families] | resemble | [one another], | |
| b: | but | [each unhappy family] | is unhappy | [in its own way]. |
How do we know that these words I have put in brackets are in fact units? In a variety of ways. For example, we can substitute a single pronoun they for “all happy families” or it for “each unhappy family.” And “in its own way” could be the answer to the question “how is each unhappy family unhappy?”
These units are constituents in the sentence. A constituent is any word or group of words that functions together as an entity. Most rules of syntax do not, in fact, apply to individual words but to larger constituents. There is no limit, in principle, to the size of a constituent. It may be one or two words, or it may be hundreds of words long.
At its heart, grammatical analysis involves deciding what the constituents are in a sentence. Syntax consists of the rules by which different constituents relate to one another, so constituency is the central issue in grammatical analysis, and in interpreting sentences in general. The most important constituents we’ll be working with are phrases, clauses, and sentences.
[1] This is a very brief and informal analysis, and we have only singled out a few of the constituents in this sentence. In other words, don’t think that this analysis is anywhere near complete.
The constituent that we will see most is the phrase. A phrase consists of a single main word, called the head of the phrase, and other words that modify or give grammatical information about the head. These other words in the phrase are called the phrase’s attributes. Informally, we might say that the head word is the main idea of the phrase.
(2) Russia’s proposal at the conference
The phrase in example (2) is talking about a kind of proposal. Russia’s and at the conference tell us what specific proposal we’re talking about. Proposal, therefore is the head word.[1]
The lexical category of the phrase’s head gives its name to phrase. Thus a noun is the head of a noun phrase (abbreviated NP), a verb the head of a verb phrase (VP), and so forth. Since proposal is a noun, (2) is a noun phrase.
| (3a) | baked him a cake | Verb Phrase (VP) |
| (3b) | fond of pecans | Adjective Phrase (AP) |
| (3c) | very quickly | Adverb Phrase (AdvP) |
| (3d) | to the lighthouse | Prepositional Phrase (PP) |
Apart from simply being a convenient way to name phrases, the relationship between the head word and the phrase type captures a significant fact of syntax: the category of the head word plays an important role in determining where in the sentence the phrase can go, as well as a variety of grammatical rules such as agreement between subject and verb.
For example, in sentence (4), contract is the head word of the NP which is the subject. The whole subject, therefore is singular, and agrees with the verb was, despite the two plural nouns (boards and companies) which are closer to the verb in terms of linear order, but which are actually buried in prepositional phrases.[2]
This example also illustrates another important point: phrase structure is hierarchical. That is, phrases can nest within phrases to any level of complexity. Thus the subject of (4), “the agreement between the boards of the two companies,” contains two prepositional phrases, each of which itself contains a noun phrase. We can show this relationship in a diagram:
Take a moment to study this diagram. We will refine it later with additional details, but it’s important that you recognize what information it’s trying to communicate. It shows that the whole noun phrase contains three parts: a determiner, the, the head noun, agreement, and a prepositional phrase, between the boards of the two companies. In turn, that prepositional phrase consists of its head word, between and a noun phrase, the boards of the two companies. That noun phrase contains yet another prepositional phrase, of the two companies, which contains its own noun phrase, the two companies. That’s what we mean when we say that phrase structure is hierarchical: one phrase can contain another phrase inside it.
Viewed this way, even the most elaborate sentence can always be broken down into a handful of relatively simple patterns that repeat over and over.
One final note on phrases: in ordinary, non-technical usage, the word phrase means “more than one word.” Thus you will sometimes encounter books that use the expression “word or phrase” to explain concepts like the subject. As we have defined phrases here, however, that expression is redundant. Because the attributes of a phrase are often optional, it is possible to have a phrase that consists of a single word.
(5) Computers intimidate many people.
(6) The young man was naïve.
In sentence (5), computers is a noun in a phrase with no attributes. It is a noun phrase all by itself. In sentence (6), naïve is a one-word adjective phrase. Treating these constituents as phrases, and not just individual words, allows us to account for many aspects of grammar in a simpler and more consistent fashion than if we treated them differently.
[1] This semantic test works reasonably well for prototypical cases, but be careful. There are many cases where the idea of the phrase won’t really match the structural head. In other words, this notional definition of the head is meant to get you started with the easy cases, but it’s only a rough guide. As you look at the examples that follow, pay attention to the structural patterns first, and meaning second.
[2] We are, of course, speaking of Standard English when we refer to subject-verb agreement rules. Some people do from time to time operate by a principle of attraction, making the verb agree with the nearest noun rather than the head noun of the whole phrase.
Labels like NP, VP, etc, tell us the structural form of a constituent. Form alone, however, does not tell us everything about how a constituent works in the sentence. We must also consider its function.
(7) Her dog chases rabbits.
For example, her dog and rabbits in (7) are both noun phrases, but they have different functions in the sentence. Although we haven’t yet specified these functional roles, we can already see that each noun phrase has a different role in the sentence. The dog is doing the chasing, and the rabbits are being chased. The role of her dog is probably already familiar to you: it serves as the subject of this sentence. Rabbits plays a role known as the direct object, which we will study in the next chapter.
(8a) His happiness was evident.
(8b) That he was happy was evident.
Although subjects are typically noun phrases, they need not be. The underlined constituents in (8a) and (8b) are both subjects, but these two subjects are realized by different forms. The first is a noun phrase while the second is a clause (another term we’re about to get to). In other words, just as the same form can serve different functions, the same function can have different forms.
(9) Shelly wrote a short story.
(10) The baseball player underwent elbow surgery.
If we consider constituents that are underlined in (9) and (10) above, we can see that they both have the same form (NP) and that they are both subjects, but in another way their functions are different. Shelly in (9) plays the role of the actor; she performs an action. The baseball player, however, is not the actor in (10); the surgery is performed upon him. He plays the role of the experiencer, commonly called the patient. (That’s the general term, and not just because this particular sentence is about a medical procedure.)
Notice that in discussing these roles, we are invoking the meaning of the sentence. They are, in other words, semantic roles, and they are not the same thing as grammatical roles like subject and direct object. Grammatical roles are defined by structural relationships within the sentence, semantic roles by relationships of meaning.
Keep in mind these distinctions. The form of a constituent, its grammatical function, and its semantic function, do not exist in one-to-one relationships. We will see many instances as we proceed where there are prototypical relationships. For example, subjects prototypically are NPs and actors. But as soon as you start to generalize and assume, for example, that subjects are always actors, you will get into trouble. You will save yourself a great deal of confusion if you distinguish form, grammatical function and semantic function carefully. As we proceed, take note of when we are discussing form and when we are discussing function.
A clause is a constituent consisting of two parts: a subject and a predicate. The concepts of subject and predicate are probably already familiar to you from your earlier schooling. In terms of meaning, we can say that the subject is the part of the clause about which something is asserted, and the predicate makes that assertion. These definitions are vague, and eventually we will need to be more precise. We will describe a clause in terms of structure once we’re better able to describe how that structure works.
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Subject and predicate are both grammatical functions. The predicate is realized by a verb phrase, and in the most common case, the subject is realized by a noun phrase. Notice that in the diagram above, we indicate both the grammatical form (the phrase type) and the function. The two are separated by a colon. Thus our notation follows the pattern form: function.[1]
One important point to note about subjects is that they frequently consist of more than one word.
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Many students are taught in grade school to identify the word senator alone as the subject. However, notice that senator is merely the head noun of the subject. The determiner the and the prepositional phrase from California are also part of the subject. In other words, subjects and predicates, along with other grammatical functions we will encounter later, are functions of phrases, not of individual words. As we noted above, however, those phrases may consist of only one word from time to time.
[1] Some theories of grammar do not mark functions as a matter of principal. Such theories attempt to give the most parsimonious account possible, and in this way of looking at things, grammatical roles such as subject are predictable from the structure. Although it may be redundant to mark such roles, we do so here for pedagogical reasons. We are primarily interested in describing all the relevant grammatical features in a way that is relatively easy to interpret, and to that end, we will tolerate a certain amount of redundancy.
Traditional grammar books, especially in their early chapters, often give the definition for the clause that we used in the previous section as the definition for a sentence. That simplification works for simple sentences, which often consist of only a single clause, but will not hold up under scrutiny:
(13a) George seems quite relieved.
(13b) It’s obvious George seems quite relieved.
(13c) George seems quite relieved, but his brother remains uneasy.
In each example, George seems quite relieved is a clause. But only in (13a) is the clause equivalent to the sentence. In (13b), the clause is embedded into a larger sentence. It is known as a subordinate clause. In example (13c), the clause is linked by coordination to another clause, but neither one is contained inside the other. In the next few chapters, we will be dealing with simple, one-clause sentences like (13a), but it’s important to keep in mind that real sentences frequently contain more than one clause. We will return to multi-clause sentences after developing an understanding of basic clauses.
Another understanding of the sentence commonly found in traditional grammars defines a sentence to be a group of words that expresses a complete thought. Like the notional definitions of parts of speech, though, this leaves much to be desired. How can (13a) count as a complete thought while the identical string of words in (13b) and (13c) do not? How do we tell what counts as a complete thought? The more we think about it, the emptier this definition appears.
(14a) The founding of the college by Leland Stanford.
(14b) Leland Stanford founded the college.
Most people would have no problem saying that (14b) is a sentence while (14a) is not, but do they not contain all the same information? And why do we even think that (14a) is complete? If this sentence appeared in a larger essay, would it not be reasonable to claim that the whole essay expresses the writer’s complete thought, and that this sentence is just a fragment of that thought? The traditional definition relies on a preexisting intuition of what constitutes a sentence. In other words, it takes for granted that we understand what it means to be complete without ever actually defining completeness.
For the moment, we will define the sentence negatively and say that it consists of at least one clause that is not contained in a larger grammatical unit. That is, if we look at texts that contain multiple sentences, the only relationship among sentences is one of simple sequence, as sentences are placed one after another.[1] Note that there are additional restrictions on what is and is not a sentence, but they will be easier to define after we have studied more types of phrases and clauses.
[1] We are not considering here the “orthographic” sentence—that is a string of words that begins with a capital letter and ends with a period, question mark, or exclamation point. While this often, especially in formal writing, aligns with syntactic sentences, the two do not necessarily coincide.
William Powell: So I’m a hero … I was shot twice in the Tribune.
Myrna Loy: I read where you were shot five times in the Tabloids.
Powell: It’s not true … he didn’t come anywhere near my Tabloids.”
—From “The Thin Man”
Many jokes, such as the banter between William Powell and Myrna Loy above, depend on an ambiguity in the sentence structure. Loy means that she read the story in the Tabloids, but Powell plays on the idea that he was shot in the Tabloids, and therefore that the tabloids are a body part. In effect, Powell reanalyzes the original statement in order to make his joke. Such ambiguities are frequent in all sorts of language, not just jokes.
(15) The Red Cross evacuated the refugees from Sudan.
This sentence can be interpreted as saying either that the refugees were evacuated from Sudan or that they were from Sudan. You may be predisposed to read this sentence with the first interpretation. In fact, the second version may seem as if it means the same thing. But consider sentence (15) in the following context:
After Hurricane Katrina struck the New Orleans, Maria Veracruz, a long-time worker for the Red Cross, experienced a feeling of deja vu. When she arrived in the stricken city, she saw faces that she had encountered only six months before on the dusty plains of East Africa. With full appreciation of the irony, the Red Cross evacuated the refugees from Sudan for a second time.
With this larger context, we are now primed to read the sentence according to the second grouping. But whichever interpretation we apply to (15), it’s important to notice that our interpretation is reflected in the constituency of the items in the sentence. We can show the structure of each interpretation visually by means of diagrams:
The first diagram shows a line extending from the prepositional phrase (PP) to the noun phrase (NP), indicating that the prepositional phrase is part of (i.e., a constituent of) the noun phrase. This grouping reflects the second interpretation above. Notice that not only does it imply a particular meaning—the refugees are originally from Sudan—but it also indicates that the complete string of words, the refugees from Sudan, acts as a unit. So, for example, if we ask, “Who did the Red Cross evacuate?” we would answer “The refugees from Sudan.” Or if we expressed the idea in the passive voice, we would say
(15a) The refugees from Sudan were evacuated by the Red Cross.
The second diagram shows a line extending from the prepositional phrase directly to the verb phrase. This diagram reflects the first interpretation above: the refugees are evacuated from Sudan. By connecting the line directly to the verb phrase, we indicate that from Sudan gives information that modifies the verb evacuated rather than the noun refugees. Notice that in this interpretation, the noun phrase the refugees is also part of the verb phrase, but the noun phrase and the prepositional phrase do not form a single unit. For example, the passive form would be
(15b) The refugees were evacuated from Sudan by the Red Cross.
In other words, the string of words the refugees from Sudan does not behave as a single structural unit (constituent) under this reading of the sentence.
Sometimes, particularly once you become more familiar with syntax, the constituency of words in a sentence will be intuitively obvious. At other times, however, you will need to think carefully. To tell if words are constituents, if they are working together or not, you can try several tests.
Substitution is a particularly good test. If you can replace the candidate phrase with a pronoun (e.g., they or it) it’s a noun phrase:
(16a) The golfers were forced off the course by the approaching lightning.
(16b) They were forced off the course by the approaching lightning.
Verb phrases can usually be replaced with do so:
(17) Yolanda has saved for retirement since her 20s. John has done so only since he married.
Prepositional phrases can often be replaced by a single word (traditionally identified as an adverb):
(18a) She went to the bar.
(18b) She went there.
You can also demonstrate phrase structure if the words will move as a unit. In other words, it is often possible to recast a sentence so that it still has more or less the same meaning but so that its elements appear in a different order. Sometimes, you can do this by simple rearrangement:
(19a) They found their guest waiting in the den.
(19b) In the den, they found their guest waiting.
Movement can also be shown by creating a so-called “wh-cleft” sentence.[1] Wh-cleft sentences are formed by rearranging a basic sentence in this fashion:
(20a) That woman left her abusive husband.
(20b) Her abusive husband is whom that woman left.
The cleft sentence has the form:
moved item + form of TO BE + wh-word + clause
Notice that only phrases move—you can’t cleft a single word, or any other string of words that doesn’t constitute a phrase:
(20c) *Husband is whom that woman left her abusive.
(20d) *Abusive husband is whom that woman left her.
(20e) *Her abusive is whom that woman left husband.
One other test that often works is to see if the candidate phrase could be the answer to a (normal) question.
(21) Where did they find their guest? In the den.
But there is no natural question about the content of the sentence that could elicit “found their” as an answer.[2]
These tests for constituency are important to understand when you come to analyze sentences for yourself, so it’s a good idea to take some time to make sure you fully understand how to apply them.
[1] The name comes from the presence of a wh- word (who, why, etc.). There are also other types of cleft sentences.
[2] Of course you can ask questions such as “what are the second and third words of the sentence,” but those aren’t sentences about the content of the sentence.
Two of the most important constituents to identify are the subject and the predicate. In simple sentences, finding the subject is intuitively obvious. In elaborate sentences, we need to be more systematic. We can find the subject of even the most complex sentences by noticing a property of English grammar.
(22a) Samantha was expecting a phone call.
(22b) Was Samantha expecting a phone call?
(23a) He has been cheating on his wife again.
(23b) Has he been cheating on his wife again?
(24a) The senator could retire after the current session.
(24b) Could the senator retire after the current session?
(25a) That talented writer is a drunken sot.
(25b) Is that talented writer a drunken sot?
If we think of questions as being formed from the equivalent statement, we can see that yes-no questions are formed by moving the italicized verb from one side of the subject to the other.[1] The verbs that move are either auxiliary verbs or a form of the verb to be.
We can use this fact of English grammar as a test for our subjects. Simply turn the clause into a yes-no question (or if it’s already a question, change it to a statement) and observe the position of the moving verb. This technique will work even when the subject is very long and contains many elements inside it:[2]
(26a) The man who walked barefoot for ten miles across the burning-hot desert is thirsty.
(26b) Is the man who walked barefoot for ten miles across the burning-hot desert thirsty?
Sometimes the statement form of a sentence doesn’t have an auxiliary verb. In this case, a dummy verb, a form of the verb to do, is inserted:
(27a) Bob thinks he is a good musician.
(27b) Does Bob think he is a good musician?
Although it may seem that this process violates the general pattern, there is an alternate form that we can use when we want to emphasize a point, perhaps when responding to someone else’s assertion that Bob is not confident in his musical abilities:
(27c) Bob does think he is a good musician.
So even here, we can apply our subject-finding test, by contrasting the yes-no question with the emphatic form rather than the plain statement.
Once we have identified the subject, the rest of the clause is the predicate.
[1] The technical term for the verb that moves is the operator.
[2] There are some sentences (other than questions), where the ordinary order of subject and verb is inverted (e.g., “From his workshop have come many outstanding paintings.”) In such cases, this test becomes a little more complicated. Turning this into a question will require significant reordering (“Have many outstanding paintings come from his workshop?”) Notice, though, that the question form forces the actual subject (“many outstanding paintings”) back to its default position, and we can then turn this question back into a statement that uses the more ordinary word order (“Many outstanding paintings have come from his workshop.”)
Q. Please explain how to diagram a sentence.
A. First spread the sentence out on a clean, flat surface, such as an ironing board. Then, using a sharp pencil or X-Acto knife, locate the ‘predicate,’ which indicates where the action has taken place and is usually located directly behind the gills. For example, in the sentence: ‘LaMont never would of bit a forest ranger,’ the action probably took place in a forest. Thus your diagram would be shaped like a little tree with branches sticking out of it to indicate the locations of the various particles of speech, such as your gerunds, proverbs, adjutants, etc.
—Dave Barry, Ask Mr. Language Person
Grammarians like diagrams. You may have been compelled to draw something this in school:
from Reed and Kellogg, Graded Lessons in English, p. 60
Sometimes, students spend so much time drawing diagrams that they come to think of them as all there is to grammar. So what’s the point of diagrams? Diagrams show you the constituency of sentences visually. As we have said above, constituency is one of the central issues of syntax, so diagrams make important assertions about language, but keep in mind that diagrams are only a tool, a method of showing what you understand about sentence structure that other people will be able to apprehend rapidly.
Diagrams drawn with the method illustrated above are known as Reed-Kellogg diagrams, after the authors who developed this system in the 1860s. Although such diagrams are frequently encountered in junior high and high school textbooks, they are rarely found outside the schoolroom. Of course, Reed-Kellogg diagrams are meant to be pedagogical, so that limitation is not necessarily a bad thing. They do capture a number of important features of sentence structure in a clear visual layout. In the diagram above, for example, we can quickly appreciate the core of the sentence and how the other elements relate to that core.
For the purposes of giving a truly accurate structural view of a sentence, however, Reed-Kellogg diagrams have many limitations. One drawback is that to understand these diagrams, you need to learn the significance of a relatively wide variety of different symbols. In this diagram alone we have thick horizontal line, thin horizontal lines, different kinds of slanting lines, and a dotted line. And there are a number of other symbols for structures not found in this example. More significantly, notice, in the diagram above, that determiners like the, adverbs like very, and prepositions like of are all indicated in the same way: by writing them on a slanting line. In other words, no distinction is made among these three very different word classes. As we develop our account of English syntax, we will see other ways in which Reed-Kellogg diagrams give a misleading picture of English syntax.
Linguists favor a different method for representing structure, known as a “tree diagram.” You have already seen several of these tree diagrams, but we have not stopped to look closely at them. They get their names because they look somewhat trees turned upside down, and they show the various constituents branching off. Tree diagrams are used in many disciplines other than linguistics, for example, computer science. They are very good at showing structures that are hierarchical. As language is organized this way, it is a good candidate for representation with tree diagrams. The following is an example of the sort of tree diagram that we will be using for this course:
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Tree diagrams have several advantages over Reed-Kellogg diagrams. They are drawn by following a few simple principles, so you don’t have to remember what different line shapes and orientations signify. Despite that simplicity, tree diagrams can represent phrase structure accurately. One practical disadvantage, however, is that they become unwieldy for very long sentences. In comparison, Reed-Kellogg diagrams are more compact. That is, you can more easily fit your analysis of a longer sentence on one page if you use Reed-Kellogg notation than if you use tree notation.
Both tree and Reed-Kellogg diagrams are unreasonably awkward to use in certain contexts, for example in an e-mail or on-line posting where graphics may not be available. In such places, you may also run across other attempts to show syntactic relationships using only ordinary characters. One possibility is to use labeled brackets. The brackets substitute for the lines in showing how the constituents are grouped:
[[Mozart (NP: subj)] [remains (VL) [beloved (AP: s-comp)] [by [contemporary audiences (NP: obj-prep)] (PP: agent) (VP: predicate)] (Clause)].
All the same information is here, but unfortunately, this method tends to lack visual clarity. It’s difficult to grasp the constituency of the sentence at a glance the way you can with a diagram. Still another method to indicate constituents uses horizontal lines and labels above (or below). These are a kind of flattened tree diagram, which have the advantage of saving space:[1]
We will generally use tree diagrams in this course. As long as the diagram accurately conveys the sentence structure, however, the exact diagramming scheme we use does not make too much difference.[2] The purpose of diagrams is merely to help us visualize the structure. They are the tools, not the ends, of grammatical analysis.
[1] Making such diagrams legible requires that you use a fixed-space font such as Courier rather than the more ordinary proportional fonts used by default in word processors and web pages.
[2] Note that this requirement makes Reed-Kellogg diagrams unsuitable. Their representation of verb phrases in particular is lacking.
Different textbooks present different variations on the tree diagram, depending on the details of their analysis. The basic principles, however, remain constant, and if you understand them, you should be able to grasp the diagrams’ essence no matter what the details. Tree diagrams are most often drawn above the item being diagrammed.[1] A tree consists of nodes. A node has a label, for example NP for noun phrase, VP for verb phrase, and so on. The node at the very top of the tree, the one from which all the others ultimately derive, is called the root of the tree. The nodes are connected by lines, known as edges. The terminal nodes of our diagrams, the ones without any children, are known as the leaves of the tree. They will contain labels for the word categories (parts of speech) of each word. (The following examples contain details that we haven’t introduced yet. Don’t worry about these yet. It’s only important here that you understand the general message that the diagram is meant to communicate.)
Borrowing terminology from genealogical trees, the nodes below another node are sometimes called the children of that node. A node that has children is a parent node. Just as with people, parent nodes can themselves be children of other parents. If we need to talk about nodes that are children of children, we call them descendants. Unlike genealogical trees, however, it is important to note that while a node may have several children, it only has one parent. Also, each line should connect to one child node. Do not show two edges connecting to a single word.
Further, you should always space out your nodes so that edges do not cross one another. This practice is merely for visual clarity. In principle, there’s no reason why the lines must never cross.
Sometimes, we will not want to analyze a sentence completely. Initially, we will lack the knowledge to analyze everything in a sentence. Later on, with more complex sentences, we may choose to ignore details that aren’t relevant to our purpose. In these cases, we will indicate an unanalyzed constituent by using a triangle.
An unanalyzed constituent
[1] Tree diagrams can also be drawn under the sentence, although in this course we will follow the more common practice.
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