Adverbs can be made comparative or superlative.

Different categories of adverbs have slightly different rules for becoming comparative or superlative.

	Some adverbs create the comparative and superlative with -er and -est.
	Not all adverb comparatives and superlatives use -er and -est endings. Some use the periphrastic comparative and superlatives forms of more, most; or less, least.
	Some adverbs cannot be made comparative or superlative.

more loudly

The rooster crows more loudly in the early morning than in the later morning.. 

most loudly

The rooster crows most loudly in the early morning.

louder

The rooster crows louder in the early morning that in the later morning..

loudest

The rooster crows loudest in the early morning.  

Some adverbs, such as fast and hard, have no -ly form. These adverbs have no periphrastic form. 

faster, harder

Sandra hits the ball faster and harder than any other player.

fastest, hardest

Sandra plays the fastest and the hardest in the league.

Adverbs of frequency have no comparative or superlative forms. 

  The gorilla always eats fruits.  He often eats leaves. He sometimes eats grass. He never eats meat or fish.