The adjective in this sentence is "fast"; "really" acts as an adverb.
There is no adjective in that sentence. The word "fast" is sometimes used as an adjective, but in this sentence it modifies the verb "run," so "fast" is an adverb.
fast ball
Yes. Example: He bought a fast car. Fast is an adjective describing car.
big
That black horse is running fast.
I ran really fast today. Cars go really fast.
I RANT REALLY FAST
He could do arithmetic in his head *really fast. *optional
It can be either, because there is no adverb form (fastly) for speed.A fast car (adjective)He drove fast (adverb)
no, fast is an adjective.
Speedy is a specific adjective
Yes it is. An adjective is a word that describes a noun. For example, I have a fast computer.It can also be an adverb, as in "He runs fast."Another use of the adjective or adverb is to mean tight or tightly (held fast).In a separate usage, fast is a verb (to not eat, to abstain).