With adverbs ending in -ly, you must use more to form the comparative (comparative adverbs), and most to form the superlative.
|quietly||more quietly||most quietly|
|slowly||more slowly||most slowly|
|seriously||more seriously||most seriously|
- The teacher spoke more slowly to help us to understand.
- Could you sing more quietly please?
With short adverbs that do not end in -ly comparative and superlative forms are identical to adjectives: add -er to form the comparative and -est to form the superlative. If the adverb ends in e, remove it before adding the ending.
- Jim works harder than his brother.
- Everyone in the race ran fast, but John ran the fastest of all.
Some adverbs have irregular comparative and superlative forms.
- The little boy ran farther than his friends.
- You're driving worse today than yesterday !
- He played the best of any player.
Note that it’s not possible to have comparatives or superlatives of certain adverbs, especially those of time (e.g. yesterday, daily, then), place (e.g. here, up, down), and degree (e.g. very, really, almost).