Adverbs often modify verbs, and can also modify adjectives, other adverbs, or entire clauses.
The surest way to identify adverbs is by the ways they can be used: they can modify a verb, an adjective, another adverb or even a whole clause.
- Usha soon started snoring loudly. [adverbs modifying the verbs started and snoring]
- That match was really exciting! [adverb modifying the adjective exciting]
- We don't get to play games very often. [adverb modifying the other adverb, often]
- Fortunately, it didn't rain. [adverb modifying the whole clause 'it didn't rain' by commenting on it]
Adverbs are sometimes said to describe manner or time. This is often true, but it doesn't help to distinguish adverbs from other word classes that can be used as adverbials, such as preposition phrases, noun phrases and subordinate clauses.
- Usha went up the stairs. [preposition phrase as adverbial: modifies leaves]
- She finished her work this evening. [noun phrase used as adverbial]
- She finished when the teacher got cross. [subordinate clause used as adverbial]
On the distinction between adverb and Adverbial, see the entry on the latter.