Foundations

Grammar Basics

Grammar diagrams use a small set of terms, such as subject, predicate, phrase and clause. This page defines each one and shows you how to find it in a sentence you have never seen before. Its figures draw each example twice: as a Reed-Kellogg diagram and as a dependency tree.

What you’ll learn

Tell a word, a phrase, a clause and a sentence apart
Split a clause into its subject and its predicate
Find the head of a phrase and the words that modify it
Tell a required argument from an optional adjunct with the deletion test
Tell a finite verb from a verbal, and name the phrase a verbal builds
Say what a Reed-Kellogg diagram shows that a dependency tree does not, and the reverse

Words, phrases, clauses, sentences

English sentences are built in four layers: words, phrases, clauses and sentences. Each layer is made of units from the layer below. Many grammar terms tell you which layer a group of words belongs to.

A word is the smallest unit that stands alone
Birds, sing and loudly are words. Each word belongs to a category, such as noun, verb or adverb: see Parts of Speech.
A phrase is a group of words acting as one unit
the tired birds behaves exactly like the single word birds: it can fill the same slot in a sentence. A phrase has no subject-and-verb pair of its own.
A clause has a subject and a verb
birds sing is a clause. So is when the sun rises — it has a subject (the sun) and a verb (rises), even though it cannot stand on its own.
A sentence is one or more clauses that can stand alone
Birds sing. is a sentence. When the sun rises. is not: it is a clause, but When makes it depend on another clause that is missing. A clause like this, written as if it were a sentence, is a fragment.

Subject and predicate

Every clause divides in two. The subject is what the clause is about; the predicate is what it says about the subject. This division is the first thing a Reed-Kellogg diagram draws, and almost every other word goes into one of the two parts.

Find the verb first, not the subject
The verb is easier to find: it has a present form and a past form. Put yesterday in front of the sentence and see which word must change: Birds sing → Yesterday birds sang. The word that changed, sing, is the verb. If the sentence is already about the past, use every day instead.
Then ask who or what is doing it
Say the verb aloud and put who? or what? in front of it. In Birds sing., “who sings?” answers birds. That is your subject.
Everything left over is the predicate
The predicate is the verb plus every word that belongs with it, such as its objects and its modifiers. In Wolves howl at night., the subject is Wolves and the predicate is howl at night.

“Birds sing.”

Reed-Kellogg — the base line and its vertical divider

nsubj Nominal subject
ROOT Root of the sentence

Dependency — one root, one arc

Comparing the two views

Reed-Kellogg puts the subject and the predicate side by side on one line, with the vertical line as the border. The tree has no border. It puts sing at the top as the root, the word that depends on no other. Birds hangs below it, with the label nsubj. Reed-Kellogg answers “what are the parts?”; the tree answers “what depends on what?”

Heads and modifiers

Most phrases are built around one main word, the head (in Spanish, núcleo). The other words add detail to the head; they are its modifiers.

In the heavy rain, the head is rain. Delete the or heavy and you still have rain; delete rain and nothing is left to talk about. This test (which word survives?) finds the head of most phrases. A prepositional phrase is the exception: in at night, the dependency tree makes at the head and hangs night below it.

“The heavy rain stopped.”

Reed-Kellogg — two modifiers on slants under the subject

det Determiner
amod Adjectival modifier
nsubj Nominal subject
ROOT Root of the sentence

Dependency — the same two modifiers, named

Comparing the two views

Here the two views agree. Reed-Kellogg hangs The and heavy on slants beneath rain; the tree draws arrows from rain down to the same two words. Only the names differ. The labels det (determiner) and amod (adjectival modifier) say what kind of modifier each word is; a slant just says “modifier”.

Required and optional

Some words are required by the verb; others are optional. The required ones are arguments, the optional ones adjuncts. Reed-Kellogg draws them in different places. The subject, the direct object and a complement sit on the base line, and adjuncts hang below it. The indirect object is the exception: it is an argument, but it hangs below the verb.

Maya bought bread on Sunday. Remove bread and the sentence breaks: Maya bought on Sunday is unfinished, so bread is an argument. Remove on Sunday and nothing breaks: Maya bought bread is complete, so on Sunday is an adjunct.

“Maya bought bread on Sunday.”

Reed-Kellogg — the argument on the base line, the adjunct below it

nsubj Nominal subject
ROOT Root of the sentence
dobj Direct object
prep Prepositional modifier
pobj Object of preposition

Dependency — dobj for the argument, prep for the adjunct

Comparing the two views

Reed-Kellogg shows the difference by position. The argument bread sits on the base line after a half vertical, a short line that does not cross the base line. The adjunct on Sunday hangs below the verb. The tree hangs bread and on directly from bought, so only the labels differ. The label dobj marks the direct object. The label prep marks a preposition, but not whether its phrase is required: for that, use the deletion test.

Finite and non-finite verbs

A finite verb can head a clause on its own, and it usually carries tense: sings, sang, will sing. A non-finite verb cannot — to sing, singing, sung need a finite verb somewhere nearby to anchor them.

This is why Wolves howling at night. is not a sentence but Wolves howl at night. is. The three non-finite forms each get their own topic: infinitives, gerunds and participles.

Modal verbs are finite too: can sing heads its clause. In this app it has no tense, because only will and shall give a modal verb phrase a tense. Commands such as Sing! and base-form subjunctives such as that she sing are finite as well. Their verb is a base form, yet it heads its own clause.

Verbals are phrases (non-finite clauses)

A non-finite verb is called a verbal, and it usually comes with other words. Look at to visit Peru, painting landscapes and stacked in the closet. Each one has a verbal with its own object or modifier: everything a clause has, except a subject of its own and a tense.

This app calls such a group a phrase, as most school grammars do. Its name comes from the verbal inside it: an infinitive phrase, a gerund phrase or a participial phrase. A verbal can also be a phrase on its own: To love in To love is to live fully is a one-word infinitive phrase.

A verbal phrase has most of the parts of a clause, so Reed-Kellogg draws it as a small diagram of its own. When the phrase fills a noun slot, its diagram stands on a pedestal in that slot, as in the figure below. When it modifies a word, it hangs from that word. Its object is still a Direct object, but its verb is not a Verb phrase: that name is kept for finite verbs.

The Roles exercise names the phrase by its form, and adds its job where it has one:

Infinitive phrase, plus the slot it fills — Nora wants to visit Peru is Direct object + Infinitive phrase. See Infinitives.
Adjectival, Adverbial or Complementary infinitive phrase, one label each, because the name already says the job: a place to sleep, ran to catch the bus, has to feed the cat.
Gerund phrase, plus its slot — He avoids driving at night is Direct object + Gerund phrase. See Gerunds.
Participial phrase, alone when it modifies a noun, plus its slot when it completes the verb. See Participles.
Absolute phrase for a noun with a participle of its own, attached to nothing: His chores finished, Kenny went outside.

“Nora wants to visit Peru.”

Reed-Kellogg — the infinitive phrase on a pedestal in the direct-object slot

nsubj Nominal subject
ROOT Root of the sentence
aux Auxiliary
xcomp Open clausal complement
dobj Direct object

Dependency — xcomp, with to as aux

Comparing the two views

Reed-Kellogg puts all of to visit Peru on a pedestal in the direct-object slot of wants. The diagram shows the phrase as one unit doing a noun’s job. The tree has no pedestal. It labels visit xcomp of wants, and to hangs from visit as aux. An xcomp has no subject of its own, so visit shares the subject of wants. The tree records that Nora is the one who visits.

Why every sentence is drawn twice

This app shows two diagrams for every sentence, and they are not two styles of the same picture. They answer different questions, and each is good at what the other is bad at.

Reed-Kellogg is a constituency diagram. It asks: which words group together, and what job does each group do? Its answer is a shape. Where a word sits on the lines is its job, so you can find the subject without any label.

A dependency parse asks a narrower question: for each word, which single other word does it attach to? Its answer is a set of labelled arrows. It has no mark for a phrase, although you can find one: a word plus every word below it in the tree. In exchange, it names every relationship, and it is what the computer produces when it reads a sentence.

“Wolves howl at night.”

Reed-Kellogg — the prepositional phrase is one visible unit

nsubj Nominal subject
ROOT Root of the sentence
prep Prepositional modifier
pobj Object of preposition

Dependency — two arcs, no grouping, but every relation named

Comparing the two views

Look at at night. Reed-Kellogg draws it as one shape under the verb: a diagonal for at and a horizontal for night. So you can see at once that the two words form one unit with one job. The tree never says “these two words are a phrase”. It says that at attaches to howl and night attaches to at, and you work out the group yourself. But it names the two relations, prep and pobj, which the slant does not.

Quick check

Is each of these a phrase, a clause or a sentence? (a) under the old bridge (b) while the children slept (c) The children slept.
Answer
(a) is a phrase: it has no verb, only a preposition and a noun with its modifiers. (b) is a clause, because it has a subject (the children) and a verb (slept). It cannot stand alone, though: while makes it depend on another clause. (c) is a clause that stands alone, so it is also a sentence.
In The small dog behind the fence barked., what is the subject, what is the predicate, and which word is the head of the subject?
Answer
Find the verb first: with every day in front, barked becomes barks. Then ask “what barked?” The answer, the small dog behind the fence, is the subject: all six words. The predicate is what is left, barked. The head of the subject is dog. Delete the, small or behind the fence and a dog still barks; without dog, nothing is left to bark. In the Roles exercise, the Subject box holds all six words.
In Diego borrowed a pen during the exam., which of a pen and during the exam is an argument, and which is an adjunct? Where does Reed-Kellogg draw each one, and what labels does the dependency tree give them?
Answer
Use the deletion test. Without a pen, the sentence breaks (Diego borrowed during the exam), so a pen is an argument: the direct object. Without during the exam, it is still complete, so that phrase is an adjunct. Reed-Kellogg puts pen on the base line after a half vertical and hangs during the exam below borrowed. The tree labels pen dobj and during prep.
Which verb in Lucia decided to sell her bike. is finite? What is to sell her bike, and what job does it do?
Answer
decided is finite: with every day in front, it becomes decides, and it heads the clause. to sell stays the same, so it is a verbal: an infinitive. With its object her bike, it forms an infinitive phrase, with no subject and no tense of its own. The phrase answers “decided what?”, so it fills the direct-object slot, and Reed-Kellogg stands it on a pedestal there. The Roles exercise marks it Direct object + Infinitive phrase.

Key terms

Other pages link back to these terms. For every term in the Learn section, see the Glossary.

Word: The smallest unit that can stand on its own. Every word belongs to a part-of-speech category. Birds sing loudly. is three words from three categories; the tired birds is three words doing the job of one.
Phrase: A group of words acting as a single unit, with no subject-and-verb pair of its own. the tired birds, at night, had been waiting. The tired birds slept. — the first three words fill the subject slot together.
See: Prepositional Phrases
Clause: A group of words containing a subject and a verb. An independent (main) clause can stand alone as a sentence; a dependent (subordinate) clause cannot. The sun rises. is an independent clause. when the sun rises has a subject and a verb too, but it cannot stand alone: it is a dependent clause. The Roles exercise boxes each sentence's Main clause: the whole independent clause, with any clause that depends on it inside. It names the dependent clause by its kind: noun, adjective or adverb clause.
See: Adverb Clauses · Adjective Clauses · Noun Clauses
Subject: What the clause is about — the answer to who? or what? in front of the verb. It sits left of the full vertical line. Birds sing. The old kettle whistled. — the subject can be one word or a whole phrase.
See: Subjects & Verbs
Predicate: What the clause says about its subject: the verb plus every word that belongs with it. It sits right of the full vertical line. Birds sing. — just the verb. The kettle whistled on the stove. — the verb and its phrase.
See: Subjects & Verbs
Head: The main word of a phrase. Delete the other words, and the head can still do the job of the whole phrase. In a dependency tree, every word except the root has exactly one head. In the tired birds, the head is birds. A phrase can hold a smaller one. In very tired birds, tired is the head of very tired. That group modifies birds, the head of the whole phrase.
See: Dependency Parsing
Modifier: A word or phrase that adds detail to another word without being required by it. Drawn on a slanted line beneath the word it modifies. The tired birds slept. — tired modifies birds. Birds sing loudly. — loudly modifies sing.
See: Adverbs · Articles, Adjectives & Objects
Argument: An element the verb requires: a subject, a direct object, an indirect object or a complement. Most arguments sit on the base line; the indirect object hangs below the verb. Omar needs a ladder. — drop either one and the sentence breaks. She gave him a map. — a map sits on the base line, and him, the indirect object, hangs below gave.
See: Articles, Adjectives & Objects · Indirect Objects & Complements
Adjunct: An optional element you can delete without breaking the sentence. Adjuncts hang below the base line. Birds sing at dawn. — remove at dawn and the sentence still stands. Yesterday the kettle broke. — yesterday is an adjunct too.
See: Adverbs · Prepositional Phrases
Finite verb: A verb that can head a clause by itself. Most finite verbs are inflected for tense, but some have no tense in this app: commands, base-form subjunctives and modals other than will and shall. Contrast the non-finite forms, which cannot head a clause. The kettle whistles. — present tense. The kettle whistled. — past tense; either one heads the clause alone.
See: Subjects & Verbs · Modal Auxiliaries · Tense · Mood
Non-finite verb: An infinitive, gerund or participle — a verb form carrying no tense, which needs a finite verb elsewhere in the sentence to anchor it. The kettle began to whistle. — an infinitive, anchored by began. The whistling kettle woke us. — a participle, anchored by woke.
See: Infinitives · Gerunds · Participles
Verbal phrase: An infinitive, gerund or participial phrase: a verbal with its own objects and modifiers, but no subject and no tense. Modern grammars call the same unit a non-finite clause. She hopes to visit Lisbon. Rescuing the kitten took an hour.
See: Infinitives · Gerunds · Participles
Constituency: The view of a sentence as nested groups of words, each group doing one job. This is what a Reed-Kellogg diagram draws. The tired birds slept. is [the tired birds] + [slept], with [tired] nested inside the first group. Birds sing at dawn. is [birds] + [sing at dawn].
See: Reed-Kellogg Diagrams
Dependency: The view of a sentence as a set of labelled word-to-word links. This is what the dependency tree draws, and what the parser actually computes. In Birds sing. the one link runs from sing to birds (nsubj). In The tired birds slept. every word links to exactly one other.
See: Dependency Parsing
Token: One unit as the parser counts them — usually a word, but a contraction splits into two (can’t is ca + n’t) because the halves behave differently, and each punctuation mark is a token too. We can’t stay. has five tokens, counting the full stop, but three words. Omar’s coat is here. has six tokens: Omar and ’s are counted separately, and so is the full stop.
See: Parts of Speech

Practice on a real sentence

This short sentence has the main parts this page teaches. In Roles, choose a role, then drag across the words that play it: start with the main clause, then its subject and its predicate. Inside the predicate, find the verb phrase and the direct object, the argument the verb needs. In Role match, match each ready-made phrase to its role. One question the exercises do not ask: which word is the head of the direct object?

Loading the practice sentence…