The verb is king in English. The shortest sentence contains a verb. You can make a one-word sentence with a verb, for example: "Stop!" You cannot make a one-word sentence with any other type of word.
Verbs are sometimes described as "action words". This is partly true. Many verbs give the idea of action, of "doing" something. For example, words like run, fight, do and work all convey action.
But some verbs do not give the idea of action; they give the idea of existence, of state, of "being". For example, verbs like be, exist, seem and belong all convey state.
A verb always has a subject. (In the sentence "Raju speaks English", Raju is the subject and speaks is the verb.) In simple terms, therefore, we can say that verbs are words that tell us what a subject does or is; they describe:
action (Mohan plays cricket.)
state (Lakshmi seems kind.)
There is something very special about verbs in English. Most other words (adjectives, adverbs, prepositions etc) do not change in form (although nouns can have singular and plural forms). But almost all verbs change in form. For example, the verb to work has five forms:
to work, work, works, worked, working
Of course, this is still very few forms compared to some languages which may have thirty or more forms for a single verb.
Some important Types of Verbs
An action verb expresses an activity that a person or thing can do. For example:
Krishna eats Dosa.
("Eating" is something Krishna can do.)
A stative verb expresses a state rather than an action. A stative verb typically relates to a state of being, a thought, or an emotion. For example:
I am at office.
He believes in god.
A transitive verb is one that acts on something (i.e., it has a direct object). For example:
I saw the elephant.
(Here, the direct object is "elephant.")
An intransitive verb is one that does not act on something (i.e., there is no direct object). For example:
The water fell.
An auxiliary verb (or helping verb) accompanies a main verb to help express tense, voice or mood. The most common auxiliary verbs are "be," "do," and "have" (in their various forms). Here is an example of auxiliary verb:
Ramu has eaten all the pies.
(Here, the auxiliary verb "has" helps to express tense.)
A modal verb is a type of auxiliary verb used to express ideas such as ability, possibility, permission, and obligation. The modal auxiliary verbs are "can," "could," "may," "might," "must," "ought to," "shall," "should," "will," and "would." For example:
Rohit can eat a lot of Apples.
(Here, the modal verb "can" helps to express the idea of ability.)
A phrasal verb is a verb made up of more than one word (usually two words). A phrasal verb has a main verb and another word (either a preposition or a particle). The phrasal verb usually has a meaning different to the main verb. For example:
A robber will often break a door to break in.
(Here, the phrasal verb "break in" means "to enter illegally," which is different to "break.")