The word "adverb" is a noun. An adverb, a word that modifies a verb, adjective, or adverb, is its own part of speech.
adverb
Adverb
Adverb
adverb
"Ever" is an adverb.
about is a adverb.
adverb
Twice is an adverb.
Commonly is an adverb.
Beautifully is an adverb.
Hysterically is an adverb.
adverb