Verbs

Intuition [Beginner]

A verb is a word that describes an action or a state. It tells you what is happening. "The dog runs." "The sky is blue." "She thought about lunch." Every sentence needs at least one verb -- without one, nothing is happening.

Verbs are the engine of a sentence. Nouns name the players; verbs say what the players do. "The bird sang." The bird is the noun. "Sang" is the verb. It is the difference between a still photograph and a movie.

Visual [Beginner]

Actions                        States
  run    jump    eat             be     seem    feel
  write  build   throw          exist  appear  know
  sing   drive   read           belong remain  love

The left column lists things someone does. The right column lists things someone is or experiences. Both are verbs. Actions are easier to spot; states can be trickier because nothing visible is happening, but "is," "seems," and "knows" are verbs just as much as "runs" and "jumps."

Worked example [Beginner]

Find the verbs: "The cat sat on the mat and stared at the window."

• sat -- what the cat did (action)
• stared -- what the cat did (action)

"On," "at," and "the" are not verbs. "Cat," "mat," and "window" are nouns. The verbs tell you what happened: the cat sat and then stared.

What this tells us: verbs answer the question "what happened?" or "what does it do?" in a sentence.

Check your understanding [Beginner]

Formal definition [Intermediate+]

A verb is a word that expresses an action, occurrence, or state of being and that can function as the head of a verb phrase. In English, verbs are the word class that:

1. Inflects for tense: walk/walked (present/past)
2. Shows agreement with the subject in person and number (limited in English): I walk / she walks
3. Can be marked for aspect and mood: is walking (progressive), walked (perfect), walk! (imperative)
4. Occupies the predicator position in clause structure

Main verbs and auxiliary verbs

Main verbs carry the lexical meaning: run, think, build, know.

Auxiliary verbs (or "helping verbs") support the main verb by adding tense, aspect, mood, or voice:

• Primary auxiliaries: be, have, do -- "She is running," "They have finished," "I do understand"
• Modal auxiliaries: can, could, will, would, shall, should, may, might, must -- "You must leave"

A verb phrase can chain auxiliaries: "She will have been working." The main verb is work; the auxiliaries carry tense, aspect, and mood.

Transitive and intransitive verbs

Transitive verbs require a direct object: "She threw the ball." Without the object ("She threw"), the sentence feels incomplete.

Intransitive verbs do not take a direct object: "He arrived." You cannot "arrive something."

Some verbs are ditransitive, taking two objects: "She gave him the book" -- indirect object (him) and direct object (the book).

Many verbs shift between transitive and intransitive use: "I eat" (intransitive) vs. "I eat rice" (transitive). This is called the ergative alternation in linguistics.

Counter-examples to common slips

• Not every -ing word is a verb. "The running water" -- "running" modifies "water" (a participle functioning as an adjective). "I enjoy running" -- "running" is a gerund (a verb form functioning as a noun).
• Not every past-tense -ed word is a verb. "A learned scholar" -- "learned" here is an adjective derived from the verb but functioning to describe the noun.
• Imperatives have an implied subject. "Sit down" means "You sit down." The verb is "sit"; the subject "you" is understood.

Key concepts [Intermediate+]

Verb tense

English has two morphological tenses (marked on the verb itself):

• Present: walk/walks
• Past: walked

Other time references use auxiliaries:

• Future: will walk
• Present perfect: has walked
• Past perfect: had walked
• Future perfect: will have walked

The relationship between tense (grammatical marking) and time (actual when) is not one-to-one. "I am leaving tomorrow" uses present tense to describe future time. "If I knew, I would tell you" uses past tense to describe a hypothetical present. Tense is grammar; time is meaning.

Verb aspect

Aspect describes how an action unfolds over time, distinct from when it occurs:

• Simple: I walked -- the action as a whole
• Progressive (continuous): I was walking -- the action in progress
• Perfect: I had walked -- the action completed relative to a reference point
• Perfect progressive: I had been walking -- in-progress action viewed from a completion point

Finite and non-finite verbs

Finite verbs carry tense and can serve as the main verb of a clause: walks, walked, is.

Non-finite verbs do not carry tense and cannot serve as the main verb alone:

• Infinitive: (to) walk
• Gerund: walking (functions as a noun)
• Participle: walking / walked (functions as an adjective or in auxiliary constructions)

Linguistic theory [Master]

Vendler's aspectual classes

Vendler (1957) classified verbs into four aspectual categories based on their temporal properties:

Class	Duration	Completion	Example
States	ongoing	no endpoint	know, believe, love
Activities	ongoing	no natural endpoint	run, push, swim
Achievements	instantaneous	yes	notice, reach, break
Accomplishments	durative	natural endpoint	build a house, write a letter

This classification is not arbitrary. Each class behaves differently with temporal modifiers. You can say "she ran for an hour" (activity + duration) but not "she noticed the sign for an hour" (achievement + duration is odd without shifting the meaning). These distributional facts are evidence that aspectual class is a real grammatical property, not just a semantic intuition.

Thematic roles and argument structure

Every verb defines a set of thematic roles (also called theta-roles or participant roles) that its arguments must fill. "Give" requires three: an agent (the giver), a theme (the thing given), and a recipient (the receiver). The verb's argument structure specifies how many and what kind of arguments it takes.

The Theta Criterion (Chomsky 1981) states that each argument bears exactly one thematic role and each thematic role is assigned to exactly one argument. Violations produce ungrammaticality: "She gave the book" is incomplete (missing the recipient role); "She gave gave the book" is incoherent (one argument, two roles).

Verbs as predicates

In formal semantics, a verb denotes a predicate -- a function from individuals to truth values. "Runs" corresponds to $\lambda x.runs(x)$, a function that takes an individual and returns true if that individual runs. This view treats verbs as the semantic backbone of clause structure: the verb provides the predicate, the noun phrases provide the arguments, and the sentence asserts that the predicate holds of those arguments.

The formal connection: a transitive verb like "loves" corresponds to $\lambda y.\lambda x.loves(x,y)$ -- a curried function taking two arguments in sequence. This is the basis of Montague semantics and connects directly to the lambda calculus and type theory used in the math and logic units.

Historical context [Master]

"Verb" derives from Latin verbum (word), reflecting the Roman grammarians' view that the verb is the most important word in the sentence. The Greek grammatical tradition (Dionysius Thrax) used rhema, meaning "that which is said" -- the predicate. The Indo-European verb system was heavily inflected for tense, aspect, mood, voice, person, and number. English has lost most of this inflection: Modern English verbs mark only tense (present/past), person (3rd singular -s), and the -ing/-ed participial forms. The lost distinctions are recovered through auxiliary verbs, which is why English verb phrases can grow long ("will have been being examined").

Bibliography [Master]

• Chomsky, N. (1981). Lectures on Government and Binding. Foris Publications.
• Vendler, Z. (1957). "Verbs and Times." The Philosophical Review, 66(2), 143-160.
• Huddleston, R. & Pullum, G. K. (2002). The Cambridge Grammar of the English Language. Cambridge University Press.
• Dowty, D. (1979). Word Meaning and Montague Grammar. Reidel.