noun a state of disuse or inactivity
noun A noun is a word that represents a person, place, thing, or idea. In this case, 'yester' is not a noun.
adjective An adjective is a word that describes or modifies a noun or pronoun. 'Yester' is an adjective when used to describe something from the previous day, as in 'yesterday'.
adverb An adverb is a word that modifies a verb, adjective, or another adverb. 'Yester' is not an adverb.