Adverbs

At the general level the adverb is definable as a grammatically distinct word class with the following properties:

(a) Its central members characteristically modify (or head phrases which modify) verbs, adjectives and other adverbs. In languages which distinguish between adjectives and adverbs the primary difference is that adjectives modify nouns (or stand in a predicative relation to noun phrases) while adverbs modify verbs; the modifiers of verbs can, to a very large degree, also modify adjectives and adverbs, so that we then extend the definition of adverb to cover modifiers of all three open classes other than nouns.

(b) Central members commonly express manner or degree; other frequent meanings (often associated with grammatically less central members) include time and place.

(c) It is commonly the case that many members, especially those belonging to the manner subclass, are morphologically derived from adjectives.

Consider now, at the language-particular level, the properties of adverbs in English.

(a) Function. Adverbs, or the phrases they head, occur in a rather wide range of functions, notably (though not exhaustively): (α) modifier in VP structure ([She spoke] clearly), (β) modifier in AdjP structure ([She's] extraordinarily [bright]); (γ) modifier in AdvP structure ([She did it] rather [well]); (δ) peripheral dependent in clause structure (Frankly, [he's a dead loss]); (ε) complement in VP structure ([They put us] ashore).