Foundations

Grammar Basics

Before any diagram makes sense, a handful of words have to mean something precise. This page defines them — and, more usefully, shows you how to find each one in a sentence you have never seen before.

What you’ll learn

Tell a word, a phrase, a clause and a sentence apart
Split any sentence into its subject and its predicate
Spot which word in a phrase is the head, and which words modify it
Tell a required element from an optional one
Recognise a non-finite clause and see where the diagram puts it
Understand why this app draws every sentence twice

Words, phrases, clauses, sentences

English builds meaning in layers. Each layer is made of the one below it, and almost every term in grammar is really a claim about which layer you are looking at.

A word is the smallest unit that stands alone
Birds. sing. loudly. Words are what you can move around, and each one belongs to a category — 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 — you can drop it into 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 leaves you waiting for the rest.

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 single division is the foundation of the whole Reed-Kellogg notation — everything else hangs off it.

Find the verb first, not the subject
The verb is the easier target: it is the word that changes with tense. Try putting yesterday in front of the sentence and see which word wants to change.
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
Not just the verb — the predicate is the verb plus whatever travels with it.

“Birds sing.”

Reed-Kellogg — the base line and its vertical divider

nsubjNominal subject
ROOTRoot of the sentence

Dependency — one root, one arc

Comparing the two views

The two pictures say the same thing in opposite directions. Reed-Kellogg splits the sentence into two halves of equal weight — the vertical line is a boundary between subject and predicate. The dependency parse has no such boundary: it makes sing the single root and hangs Birds underneath it as an nsubj. Reed-Kellogg answers “what are the parts?”; the dependency tree answers “what depends on what?”

Heads and modifiers

Inside any phrase, one word carries the meaning and the rest lean on it. The essential word is the head; the words that add to it are 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. That test — which word survives? — is how you find a head every time.

“The heavy rain stopped.”

Reed-Kellogg — two modifiers on slants under the subject

detDeterminer
amodAdjectival modifier
nsubjNominal subject
ROOTRoot of the sentence

Dependency — the same two modifiers, named

Comparing the two views

Here the two views agree closely, which is worth seeing at least once. Reed-Kellogg hangs The and heavy on slants beneath rain; the dependency parse draws arcs from rain down to the same two words, labelled det and amod. The difference is vocabulary, not analysis: the dependency labels name what kind of modifier each one is, while the slant just says “modifier”.

Required and optional

Some words a verb cannot do without; others it merely tolerates. The required ones are arguments, the optional ones adjuncts. The distinction matters because Reed-Kellogg puts them in completely different places: arguments sit on the base line, adjuncts hang below it.

Maya baked bread. — remove bread and the sentence feels unfinished, so it is an argument. Add on Sunday and remove it again, and nothing breaks: an adjunct.

“Maya baked bread.”

Reed-Kellogg — a half-vertical marks the direct object

nsubjNominal subject
ROOTRoot of the sentence
dobjDirect object

Dependency — dobj names the required argument

Comparing the two views

Reed-Kellogg marks the difference with the height of the divider: a full vertical separates subject from predicate, while a half vertical — one that stops at the base line — separates the verb from its direct object. The dependency parse marks it with the label instead: dobj tells you bread is a required argument, and a word like quickly would have arrived as advmod. Same distinction, encoded in shape versus in name.

Finite and non-finite verbs

A finite verb carries tense and can head a clause on its own: 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.

Non-finite clauses

A non-finite verb rarely travels alone. to visit Peru, painting landscapes, stacked in the closet — each has a verb with its own object or modifier, everything a clause has except a subject of its own and a tense. That unit is a non-finite clause; the reference books also call it an infinitive phrase, a gerund phrase or a participial phrase, by the form of the verb inside it.

Because it does a noun's or a modifier's job inside the main clause, Reed-Kellogg draws it as a small diagram of its own — stood on a pedestal when it fills a noun slot, hanging from the word it modifies otherwise. The Roles exercise boxes the whole unit as Non-finite clause; the verb inside it is still a Verb phrase, and its object a Direct object of its own.

“Nora wants to visit Peru.”

Reed-Kellogg — the infinitive clause on a pedestal

nsubjNominal subject
ROOTRoot of the sentence
auxAuxiliary
xcompOpen clausal complement
dobjDirect object

Dependency — xcomp, with to as aux

Comparing the two views

Reed-Kellogg lifts to visit Peru onto a pedestal in the object slot of wants: one thing, doing a noun's job. The parser has no pedestal — it labels visit xcomp of wants, an open complement whose subject is understood to be Nora, and hangs to off it as aux. The tree shows the control relation; the diagram shows the clause as a unit.

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 — position on the page is the grammatical role, which is why you can read a subject off it without any label at all.

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 never groups words, so it cannot show you a phrase — but it names every relationship explicitly, and it is what the computer actually produces when it reads a sentence.

“Wolves howl at night.”

Reed-Kellogg — the prepositional phrase is one visible unit

nsubjNominal subject
ROOTRoot of the sentence
prepPrepositional modifier
pobjObject 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 — a diagonal carrying at with a horizontal for night — hanging under the verb, so you can see at a glance that those two words form a single unit doing a single job. The dependency parse never says “these two words are a phrase”: it says at attaches to howl and night attaches to at, and leaves you to infer the grouping. In exchange, it tells you the relationships are specifically prep and pobj, which the slant does not.

Glossary

Every term other pages in this section link back to. If a page uses a word you do not recognise, it is probably here.

Word: The smallest unit that can stand on its own and be moved around a sentence. 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 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 leaves you waiting — a dependent 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 everything travelling 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 essential word in a phrase — the one that survives when you delete the others. In a dependency parse, every word except the root has exactly one head. In the tired birds the head is birds; in very tired birds it is tired.
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, a complement. Arguments sit on the base line. Birds eat seeds. — drop either noun and the sentence breaks. She gave him a map. — gave needs both.
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 inflected for tense that can head a clause by itself. Contrast the non-finite forms, which cannot. The kettle whistles. — present tense. The kettle whistled. — past tense; either one heads the clause alone.
See: Subjects & Verbs, Modal Auxiliaries
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
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. We can’t stay. has four tokens but three words. Omar’s coat is here. has five tokens: Omar and ’s are counted separately.
See: Parts of Speech

Practice on a real sentence

Start with something small. Tag each word, then find the subject and the predicate — the two halves this whole page is about.

“Santiago has a nice watch”

Parts of speech

Give every word its coarse Universal Dependencies category.

Words 0/5Attempts 0Correct 0Time 0:00

Sentence — select a part of speech below, then click the word(s) it applies to

Santiago has a nice watch