An adverb can modify a verb.
An adverb can modify an adjective.
An adverb can also modify another adverb.
Adverbs that modify other adverbs are called intensifiers because they intensify the action. These adverbs often answer the question to what extent?
Bob walked. The verb is walked.
Bob walked quickly. The adverb quickly tells how Bob walked.
Bob walked very quickly. The adverb very tells how quickly Bob walked.
Here are some adverbs that intensify other adverbs:
very, really, extremely, too, so, more, less, nearly, almost
My sister eats her lunch slowly.
My sister eats her lunch too slowly.
That bird sings sweetly.
That bird sings so sweetly.
Sam drives fast.
Sam drives extremely fast.
Bob completely forgot to do his homework.
Bob almost completely forgot to do his homework.
I dressed warmly for the hike.
I dressed more warmly than I should have.
In each set of sentences, the second sentence has an adverb in dark print that modifies another adverb.
Remember – some adverbs modify other adverbs. These adverbs intensify the action.