It can be an adverb, as in 'things were cheaper then'. It can also be an adjective as in being at the time indicated 'the then Governor'. It can be used as a noun as 'we have not been back since then' or 'till then, goodbye'.
adverb
what part of speech is beneath
i want to know what part of speech is camping
The part of speech is a adjective
Oppose is a verb.
The part of speech for this particular word is a noun.
part of speech
The part of speech for "answer" is a noun.
what part of speech is beneath
adverb
The part of speech for "explicit" is an adjective.
The part of speech for "lecturer" is a noun.
The part of speech for "rapid" is an adjective.
The part of speech of "came" is a verb.
The part of speech for "breezy" is an adjective.
The part of speech for "buried" is a verb.
The part of speech for "indefinite" is an adjective.