Writers and speakers primarily use verbs to indicate a type of action, such as "to fly," or to indicate a general state of existence like "to live." A special type of verbs, known as a copula or linking verb, describes the subject of the sentence, commonly through the term "to be" in English. Verbs act as one of the basic building blocks of a sentence in many languages; most grammatical English sentences require at least one noun acting as a subject, and a predicate that typically includes one or more verbs.
The Form and Function of Verbs
Within a sentence, a verb usually takes either an infinitive or conjugated form. In English, the infinitive form typically includes the word "to" such as "to run" or "to jump." Conjugated verbs, however, drop the word "to" and have forms such as "runs" and "jumped" in "He runs each day" or "She jumped over the hurdle." These conjugated forms are typically inflected or changed in some way to indicate something about the sentence the verb is a part of, such as "tense" or "voice." Rules for conjugation vary from one language to another, those that follow a simple conjugation rule are called "regular" while those that do not are "irregular."
In terms of function, verbs within a sentence provide action or connect one idea to another. Using action verbs such as "run," "walk," and "swim" indicates what the subject of a sentence does, such as "He runs" or "The cat sleeps." A copula, on the other hand, connects two ideas together by equating them, such as "He is my teacher" or "The car was red." In each usage, these verbs typically come after the subject of a sentence, which they refer to or describe.
Primary and Auxiliary Verbs
Primary verbs express the main action or relationship within a sentence. In the phrase "He runs" the word "runs" indicates the action. Auxiliary verbs, on the other hand, give secondary information or help conjugate primary verbs. For example, the word "was" in the sentence "He was going to the store" is an auxiliary for the primary verb "going" and conjugates it into a new tense.
Active and Passive Voice
"Voice" indicates the focus of a verb. The most basic distinction rests between active, subject-focused sentences such as "I cooked the broccoli," and passive or object-focused sentences such as "The broccoli was cooked by me." People generally consider active voice more appealing and stronger in writing than passive voice, and writers often create active sentences by properly arranging the subject, object, and verbs within it.
Different Types of Conjugation and Inflection
"Tense" indicates the time in which an action takes place. In English this usually differentiates between the past, present, and future. For example, inflecting the verbs in the following sentences creates three different states of time: "The woman sat on the chair," or "The woman sits on the chair," or "The woman will sit on the chair." Some languages make little distinction through inflection, instead using adverbs or auxiliaries; English doesn't actually inflect between present and future tense, but uses an auxiliary to change from "sits" to "will sit."
"Aspect" describes something about the nature of the verb. This can distinguish between progressive and non-progressive, for example inflecting the sentence "I pick up the bucket" could mean someone picks up the bucket eternally, at a set time every day, or just once. It distinguishes between a static and dynamic state; a particular event as opposed to a changing situation.
"Mood" gives the verb's relationship to intent or reality. English doesn't use many moods, but it does use the indicative, describing fact and opinion as in "Ursula sat down;" the imperative, describing command or prohibition as in "Ursula, sit down;" and the subjunctive, which is pretty open-ended and includes requests like "Jim suggested Ursula sit down." Other languages make use of a negative mood, instead of using a negating word like "not," which creates statements comparable to "Ursula not-sit down."
Transitivity
Most sentences include transitive, intransitive, or reflexive verbs. Transitive verbs act upon the object of the sentence, such as "He threw the ball," in which "He" is the subject and "the ball" is the object being acted upon. Intransitive verbs, however, simply act without an object, such as "The cat slept." Reflexive verbs act on the subject itself, seen in sentences like "He threw himself down the stairs," in which a transitive verb is followed by an object that refers back to the subject.