Adverbs and adjectives have important characteristics in common — in particular their gradability, and the fact that they have comparative and superlative forms. However, an important distinguishing feature is that adverbs do not modify nouns, either attributively or predicatively:
| Adjective | Adverb |
| David is a happy child | *David is a happily child |
| David is happy | *David is happily |
The following words, together with their comparative and superlative forms, can be both adverbs and adjectives:
early, far, fast, hard, late
The following sentences illustrate the two uses of early:
| Adjective | Adverb |
| I’ll catch the early train | I awoke early this morning |
The comparative better and the superlative best, as well as some words denoting time intervals (daily, weekly, monthly), can also be adverbs or adjectives, depending on how they are used.
We have incorporated some of these words into the following exercise. See if you can distinguish between the adverbs and the adjectives.
Although endings, gradability and comparison allow us to identify many adverbs, there still remains a very large number of them which cannot be identified in this way. In fact, taken as a whole, the adverb class is the most diverse of all the word classes, and its members exhibit a very wide range of forms and functions. Many semantic classifications of adverbs have been made, but here we will concentrate on just three of the most distinctive classes, known collectively as circumstantial adverbs.