An adverb is a part of speech that normally serves to modify verbs, adjectives, other adverbs, clauses, and sentences.
Some others use the suffix -wise. It competed with a related form -ways and won out against it. In a few words, like sideways, -ways survives; words like crosswise show the transition .
Some other adverbs are identical in form to their adjectives. Otherwise, other adverbs are derived from adjectives.
The comparative and superlative forms of adverbs that are identical to their adjectives are generated by adding -er and -est. The comparative and superlative forms of most other adverbs (except in poetic forms like wiselier) use more or most. Adverbs also take comparisons with as ... as, less, and least.
The usual form pertaining to adjectives or adverbs is called the positive. Thus the three grades are positive "happy", comparative "happier", and superlative "happiest".
Other languages may form adverbs in different ways, if they are used at all:
The following examples are in English, because that is the language of this text. Examples in other languages may be added, especially to show language independent properties of adverbs.
(1) In the following examples, the adverb, as a verb-modifier, is highlighted in bold. The verb that it modifies is shown in italics.
The hopefully controversy is based on the theory that people should say I am hopeful that... instead of hopefully to start and modify a sentence. Yet, there are dozens of adverbs used in this way. Obviously this rule is illogical. So, *Hopefully, grammarians won't trash hopefully as a sentence adverb anymore.