Adverbs modify verbs, adjectives, other adverbs, and sometimes clauses and whole sentences. Adjectives modify nouns and pronouns. Be careful not to use an adjective where you need an adverb. Consider the following sentences, for instance:
The sentence needs an adverb (slowly), not an adjective (slow), to modify the verb walked.
The sentence needs an adverb (really), not an adjective (real), to modify the adjective hard. (Note that really is a substitute for very that should be avoided in formal writing.)
Note the distinctions between the adjectives good and bad and the adverbs well and badly:
Well is an adjective only when it refers to health or condition:
In the same vein, remember that adjectives modify nouns and pronouns. Do not use an adverb to modify these parts of speech.
For example, after a linking verb you may be tempted to use an adverb instead of an adjective. However, the linking verb connects its subject to a subject complement, which can be either a noun (renaming the subject) or a modifier (describing the subject). When a subject complement is a modifier it must be an adjective because it describes the subject (always a noun or pronoun). It does not modify the linking verb itself and should therefore not be an adverb:
The conjunctive adverb often serves as a transition between two independent clauses in a sentence. Some common conjunctive adverbs are therefore, however, moreover, nevertheless, consequently and furthermore. When using a conjunctive adverb at the beginning of the second independent clause, be sure to precede it with a semicolon and not a comma: