Adverbs modify verbs, adjectives, other adverbs, or entire clauses. Many adverbs end in -ly, though some do not (always, never, very, well), and some words that end in -ly are not adverbs but adjectives (friendly, lovely). One of the most common adverbs is not.

Business writers frequently communicate with strangers. [modifies the verb communicate]

How can they attract customers in an increasingly difficult economy? [modifies the adjective difficult]

They must work especially hard to avoid offending readers. [modifies the adverb hard]

Obviously, they need to weigh their words with care. [modifies the independent clause that makes up the rest of the sentence]

Adverbs often answer the questions when? where? why? how? to what extent?

Many adverbs, like many adjectives, take different forms when making comparisons: forcefully, more forcefully, most forcefully, less forcefully, least forcefully.

Of all the candidates, she speaks the most forcefully.

Conjunctive adverbs modify an entire clause, and they express the connection in meaning between that clause and the preceding clause (or sentence). More common conjunctive adverbs include however, furthermore, therefore, and likewise.