A verb is generally described as a word that represents an action. In many cases, verbs do indicate actions; words like “jump,” “fly,” “walk,” “scream,” “flirt,” and “stomp” are verbs. However, some verbs contain no action at all in their meaning. Verbs like “seem” “be,” and “believe” do not involve any movement or activity at all. A better test of whether something is a verb or not is whether it can change its form to show that it agrees with a grammatical subject (e.g., I wonder, she wonders; They are here, He is here; We help, he helps) and/or whether it can shift to show present or past time (e.g., He forgets, He forgot; We walk every day, We walked this morning). A word that we call a verb in English must be able to change its form to show person (first person singular, third person singular, etc.) and time.*
Another feature of verbs is that they can combine with “not,” or with auxiliary forms plus “not,” to create negative statements.
| I am tired! | I am not tired!/ I’m not tired. |
| I like cheese. | I do not like cheese./I don’t like cheese. |
| He runs every day. | He does not run every day./He doesn’t run every day. |
Verbs also play a crucial part in sentences, as each sentence is composed of a subject element and a verb element. The verb element always shows non-past or past time.
| SUBJECT | VERB | |
| They | left. | |
| I | know. | |
| She | is sleeping. | |
| He | forgot | to return the book. |
| The man | borrowed | a lot of money. |
| The neighbors | have been | away for three weeks. |
| I | was having | a wonderful dream. |
Modal auxiliaries (“can,” “must,” “will,” “may,” etc.) are sometimes called “verbs” (i.e., “modal auxiliary verbs”) even though they do not change form. This is because, historically, they were more like ordinary verbs with past and non-past forms, and because they currently operate like ordinary auxiliary verbs in sentences (e.g., “I did go,” “I might go,” “I will go”). Furthermore, a sentence composed of just a subject and modal auxiliary is considered a full grammatical sentence just as the sentences above are.
| SUBJECT | VERB |
| I | can. |
| She | might. |
| They | must. |
Whether or not modal auxiliaries are technically verbs, they do function as major sentence elements the way that ordinary verbs and auxiliary verbs do.
*Some “irregular verbs” do not have a past tense form that looks different from the present tense form (e.g., “quit,” “put”), but every verb has a form with “s” that is used for the third person singular (e.g., “he works,” “she works,” “it works”) in standard English.