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.
adverb
about is a adverb.
Supposedly is an adverb.
Steadily is an adverb.
adverb
Commonly is an adverb.
Twice is an adverb.