Combined with its subject , the verb becomes the central element of a sentence or clause.  A main verb is the head word of a verb phrase - sometimes called a verb chain , e.g. 'He hit him hard.'  A lexical verb is the part of the verb chain that suggests the action involved, e.g. He might have hit him. A verb that tells of a 'state of being' is a copular or stative verb, e.g. is, was, seems, appears, becomes, etc. Verbs that work along with a subject are called finite (e.g. the girl looked). But verbs do not have to work with a subject within a sentence - these are called a verb's non-finite forms (e.g. I like to run). Non-finite forms of verbs can act as other parts of speech:     

The infinitive from of the verb (often used with 'to'), e.g. 'He used to love me.'

The -ed participle form (usually ending with the suffix -ed):

  • 'Only the cooked apples should be used.'

The -ing participle form:

  • 'He used cooking apples' (adjective).

  • 'The cooking was superb' (noun).

  • 'He will be cooking this evening' (continuous aspect).

A verb phrase has a head word that is a main verb along with one or more 'helper' or auxiliary verbs.

A verb phrase is a coherent group of words that acts as a unit of meaning and which most often follows a subject (which is usually a noun phrase). Along with its subject the combination forms a clause. Both single verbs and verb chains tell what the action or state of their subject.

In a verb phrase, the main verb can be inflected to show tense (e.g. eat, eaten, ate), agreement (e.g. I eat, she eats) or continuous action (e.g. He is eating) and it can also be pre-modified with an adverb (e.g. He is quietly eating) the auxiliary verb can be inverted to form a question (e.g. Do you eat spaghetti?), e.g. 'She will have been singing for forty minutes.'

» Linguistic Library (Mike Green)