Adverb

Definition:

The part of speech (or word class) that is primarily used to modify a verb, adjective, or other adverb. adverbs can also modify prepositional phrases, subordinate clauses, and complete sentences.

Position of an Adverb:

An adverb that modifies an adjective ("quite sad") or another adverb ("very carelessly") appears immediately in front of the word it modifies. An adverb that modifies a verb is generally more flexible : it may appear before or after the verb it modifies ("softly she sang"or "sang softly"), or it may appear at the beginning of the sentence ("softly she sang to the baby"). The position of the adverb may have an effect on the meaning of the sentence.

Functions of an Adverb:

Adverbs typically add information about time (rarely, frequently, tomorrow), manner (slowly, quickly, willingly), or place (here, there, everywhere) in addition to wide range of other meanings.

Adverb Clause is a dependent clause used as an adverb within a sentence to indicate time, place, condition, contrast, concession, reason, pupose, or result.

Adverb phrase is a word group with an adverb as its head. this adverb may be accompanied by modifiers or qualifiers. An adverb phrase can modify a verb, an adjective, or another adverb, and it can appear in a number of different positions in a sentence.

Source: http://grammar.about.com/od/ab/g/adverbterm.htm