Verbs

Verb forms

Verbs in English can take the various forms listed in (1).

(1)     Name of form
(alternate name) 		Description Examples
Bare Default form in present tense sentences. They play together.
I see.
Also appears in various nonfinite contexts, such as in to infinitive clauses, I want to play.
They would like to see you.
after modals, They may play.
We will see.
and in connection with do support. They don't play lacrosse.
Do you see?
-ing
(present participle) 		Combines with auxiliary be to express various aspectual nuances. The cat is playing with the yarn.
I was seeing her until she left town.
Also occurs on its own as the gerund. Playing with yarn is dangerous for cats.
We always enjoy seeing you.
-s Special form used in the present tense to mark agreement with a third person singular subject. Lukas plays with sand for hours.
The cat sees a mouse.
-ed
(past tense)		 Expresses past tense. The cat played with the yarn.
We saw a deer.
-en
(past participle) 		Combines with auxiliary be to form passives. Baseball is played all over the world.
She was last seen off Mozambique.
Combines with auxiliary have to form perfect forms. They have never played lacrosse.
I have seen it many times.

For all verbs, the -ing form is predictable from the bare form, being derived from it by the affixation of -ing (play-ing, see-ing, hav-ing, be-ing). The -s form is similarly predictable for most verbs, with major (be, is) or minor (have, has) exceptions. Finally, the past tense and past participle forms are predictable from the bare form in some cases, but not in others. With regular verbs, the past tense and past participle forms are homonyms and are formed by affixing -ed to the bare form. Why bother distinguishing between the two forms? The reason is that they are distinct for irregular verbs such as go, see, sing, or write (past tense went, saw, sang, wrote versus past participle gone, seen, sung, written).

A verb's bare form, past tense form, and past participle (in other words, exactly the forms that aren't predictable in general) are known as its principal parts.

Finiteness

The verb forms just discussed are classified into two categories: finite and nonfinite. The basic difference between the two categories is that finite verbs can function on their own as the core of an independent sentence, whereas nonfinite verbs must combine with some sort of auxiliary element (see Modals and auxiliary verbs in English for more information).

A verb's -s form and its past tense form are always finite, and the two participles (the -ing and -en forms) are always nonfinite.

(2) a. Finite verb: ok She gives both of them a back rub.
b. ok She gave both of them a back rub.
(3) a. Nonfinite verb: ok She is giving both of them a back rub.
b. ok She has given both of them a back rub.

To complicate matters a bit, the bare form can be either finite or nonfinite, as illustrated in (4) and (5).

(4)   Finite verb: ok We give both of them a back rub.
(5) a. Nonfinite verb: ok We will give both of them a back rub.
b. ok We promised to give both of them a back rub.

How can we tell whether a bare form is finite or not? Notice what happens when we replace the subjects in (2) by a third-person singular subject. The bare form of the verb is ungrammatical and needs to be replaced by the -s form.

(6) a. * She give both of them a back rub.
b. ok She gives both of them a back rub.

This fact provides us with a test for whether a bare verb form is finite or not. We simply replace the subject of the sentence by a third-person singular subject. If the bare verb must be replaced by the verb's -s form, then the bare verb is a finite verb; if not, then it is nonfinite. This test is illustrated in (7); the verb form under consideration is underlined.

Change in form? Finite?
(7) a.   I file those reports. ---> He files those reports. yes yes
b.   I promise to file those reports. ---> He promises to file those reports. yes yes
c.   I promise to file those reports. ---> He promises to file those reports. no no
d.   I might file those reports. ---> He might file those reports. no no

(8) summarizes the correlation between a verb's forms and their finiteness.

(8)     Verb form Example Finite?
Default present tense play-s, see-s yes
Past tense play-ed, saw yes
Present participle play-ing, see-ing no
Past participle play-ed, se-en no
Bare play, see depends