For most students, syntax seems very complicated and difficult, but it’s actually very easy. You need to know a few things, however, and knowing them may require some memorization and practice. On an exam, you will be expected to be able to diagram sentences correctly, but you will not be asked explicitly about any of the terminology or rules that I outline here. You therefore need to know the terminology and rules outlined here only in so far as they enable you to diagram sentences correctly.

You need to know the lexical categories of words (what used to be called "parts of speech"). English only has eleven categories altogether:

To do diagramming, you have to be able to identify the categories of all the words in a sentence. If you’ve had trouble in the past figuring out parts of speech, don’t worry. There are some easy tricks that can help you do it.

If you’re trying to figure out if a word is a noun, for example, try making it plural or possessive ("cows" or "Melvin’s"). If there is neither a plural nor a possessive, it probably isn’t a noun. If you want to be extra sure, try putting the word with a determiner ("my cow" or "a Melvin").

If you’re trying to figure out if a word is a verb, try making it past tense or try adding "-ing" ("prioritized" or "sinking"). If there is no past tense and no "-ing" form, it probably isn’t a verb. If you want to be extra sure, try putting the word with an auxiliary ("may prioritize" or "could sink").

If you’re trying to figure out if a word is an adjective or adverb, try making it into a comparative or superlative ("more importantly" or "prettiest"). If it doesn’t work, the word probably isn’t an adjective or adverb. If you want to be extra sure, try putting the word with a degree word ("very importantly" or "quite pretty").

Most people don’t have too much trouble identifying the other categories, although many people have to memorize which words are determiners, which are qualifiers, and which are degree words in order to keep those categories straight.

The XP rule says that all phrases in English consist of a head, sometimes preceded by a specifier, sometimes followed by a complement, sometimes both. In the noun phrase "the boy with glasses," for example, the head is the noun ("boy"), which is preceded by a specifier ("the") and followed by a complement ("with glasses"). Because the head is a noun, the phrase is a noun phrase.

The XP rule is a very simple and useful rule. Whenever you are confronted with a phrase (including a sentence to diagram), you know that the phrase is going to follow the XP rule and have a head, which may or may not be preceded by a specifier and may or may not be followed by a complement. You just have to figure out which part of the phrase is what in the XP rule.

The XP rule is usually written:

XP ®   (Specifier) X (Complement).

This notation just means that an XP breaks down into an optional specifier (parentheses in the rule indicate that something is optional), plus an X (the head), plus an optional complement.

So, any phrase can be broken down into its parts and diagrammed according to the XP rule.

Nouns, verbs, adjectives, adverbs, prepositions, and complementizers are the only lexical categories to function as heads in phrases (and sometimes the other categories – determiners, qualifiers, degree words, auxiliaries, and such – are therefore referred to as non-lexical). So, we’ll talk a lot about whether a phrase is a noun phrase (NP), verb phrase (VP), adjective/adverb phrase (AP), prepositional phrase (PP), or complementizer phrase (CP). For each of those kinds of phrases, there are different possibilities for specifiers and complements to go with the different heads. You’ll have to work at keeping them all straight. Determiners do not go with verbs; degree words do not go with nouns; qualifiers do not go with prepositions; etc. The chart below is a pretty complete list of all possible heads, specifiers, and complements (although I don’t guarantee that the chart is absolutely exhaustive):

Note that complements are always phrases, never single words. Even if a complement consists of a single word, you must treat it as a phrase – as in "with Tommy" which breaks down into

PP à   P NP.

In such a case, treat "Tommy" as an NP that simply consists of a single noun by itself.

There are three kinds of noun phrase (NP) that are unusual. Instead of always following the XP rule, an NP can sometimes take three other forms:

NP ®   Pronoun
NP ®   CP
NP ®   VP

For example,

she		NP ®   Pronoun
that John liked Sarah		NP ®   CP
going to the movies		NP ®   VP

Don’t forget or get confused by these exceptions to the XP rule.

Not to be outdone by the exceptional NPs, there is one kind of verb that is a little unusual.  In English, our infinitives (verbs when they aren't marked with any tense or mood) consist of two words instead of one.  For example, "to read" and "to learn" are verbs and operate as though they were single words.  So, when you see "to" and a verb ("to be," "to sleep," "to dream"), treat it as a single word -- a V.

Some examples of phrases include:

Diagramming sentences is just a matter of breaking a sentence down into the phrases that make it up, and then breaking those phrases down into their parts (specifiers, heads, and complements), and breaking all complements down into their parts (specifiers, heads, and complements), and so on and so on.

A sentence (S) itself follows the XP rule, but it’s an odd sort of XP, because its head is an odd sort of head. In a sentence, the head is the inflection (Infl) of the sentence (its tense/mood or auxiliary); the specifier is an NP (what is usually called the subject of the sentence); and the complement is a VP (what is usually called the predicate of the sentence):

S ®   NP Infl VP

The inflection is not necessarily even a word. It is usually the tense and mood of the sentence (present, past, imperative, perfect, conditional, future, subjunctive). Sometimes (but not always), the mood/tense of the sentence will be indicated by the addition of an auxiliary, which then is the inflection of the sentence (as in "The clock will strike twelve" – where "will" indicates future tense and is therefore the inflection of the sentence).

Some examples include:

Once you have broken a sentence down into its NP, Infl, and VP, you have to break down the NP and VP into their parts (specifier, head, and complements) and their complements into their parts, etc.

Modifiers are either single words or phrases that can be put into other phrases. Adjectives (and adjective phrases) modify nouns in noun phrases. Adverbs (and adverb phrases) modify verbs in verb phrases. (On rare, rare occasions an adverb or adverb phrase may modify an adjective in an adjective phrase.)

So, in addition to a specifier, head, and complement, NPs and VPs may also have a modifier (either just a single word or an entire phrase), which can go either before or after the head. For example,

the blue hen		NP ®   Det Adj N
slowly fell		VP ®   Adv V
fell slowly		VP ®   V Adv
ran slowly for a racehorse		VP ®   V AP
BUT
ran slowly through the fence		VP ®   V Adv PP

Modifiers are different from specifiers for many reasons. Most importantly, you can never have two specifiers ("the a desk" or "her this house"), but you can have a specifier and a modifier ("the blue desk" or "her old house"), as well as multiple modifiers ("slowly, painfully rises" or "the blue, speckled fish").

Note: Many of these words are not exclusively prepositions and may function in other capacities (depending on the sense of the sentence). The word "but," for example, is a preposition in the phrase "nothing but a jerk," but it’s a conjunction in this sentence. The word "like" is often a preposition ("a friend like you"), but it can also be a verb ("I like you"). The word "past" can be a preposition ("past the corner"), but it can also be a noun ("her past") or an adjective ("his past mistakes"). Both "for" and "since" function sometimes as prepositions ("since this morning," "for the party") and sometimes as conjunctions ("since he was four," "for she did not understand").  Just keep in mind, prepositions almost always have NPs as complements -- never entire sentences.

Phrasal Prepositions
(phrases of two or more words that should be treated as a single word)

Specifiers
(a handy list, but I make no guarantees that this list is absolutely exhaustive.)

Qualifiers (Qual)	always	always works
	perhaps	perhaps helps
	not	not hinder
	never	never understands
	often	often thinks
	sometimes	sometimes operates
	ever	ever spoke
Determiners (Det)	a	a house
	the	the yard
	this	this dog
	that	that cat
	these	these boys
	their	their answer
	Betty’s	Betty’s job
	Melvin’s	Melvin’s house
	its	its hair
	those	those girls
	my	my home
	his	his place
	her	her room
	your	your answer
Degree Words (Deg)	too	too heavy
	so	so flat
	very	very careful
	more	more thoughtful
	most	most difficult
	quite	quite useful

Make a tree diagram for the following phrases and sentences.

1. the bag
2. into the ocean
3. walks through the trees
4. understands difficult concepts
5. his little problem with his health
6. The exam will test material from the book.
7. John’s friend needs a bit of luck.
8. The path to success has potholes.
9. People learn from their mistakes.
10. I own the best restaurant in town for pasta.

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