Why "fast" is a adverb in "don't drive so fast"?

[unknownperson]

If that "beautiful" in "She's so beautiful" is a adjective is right, then, why "fast" is a adverb in "don't drive so fast"?:-D

 

[Rover_KE]

The word 'fast' can be either an adjective or an adverb. Click here to read its definitions.

 

[MikeNewYork]

If that "beautiful" in "She's so beautiful" is a adjective is right, then, why "fast" is a adverb in "don't drive so fast"?:-D

In the first example, the sentence's verb is a linking verb. It takes a predicate adjective (beautiful), which describes the subject.
In the second example, the sentence's verb is not a linking verb. The word "fast" modifies the verb "drive"; it is, therefore, an adverb in that use.

 

[hoangthi]

His driving is so fast -> fast is an adj. He drives so fast -> fast is an adv. That is correct ?

 

[MikeNewYork]

His driving is so fast -> fast is an adj. He drives so fast -> fast is an adv.

Exactly!

 

[unknownperson]

It make sense!