wilderness vs frontier

wilderness and frontier both are nouns.

Word	Noun	Adjective	Verb	Adverb
wilderness	Yes	No	No	No
frontier	Yes	No	No	No

As nouns, frontier is a hyponym of wilderness; that is, frontier is a word with a more specific, narrower meaning than wilderness:

Other hyponyms of wilderness include barren, waste, wasteland, bush.

wilderness (noun)	frontier (noun)
a bewildering profusion	an undeveloped field of study; a topic inviting research and development
a wild and uninhabited area left in its natural condition	a wilderness at the edge of a settled area of a country
(politics) a state of disfavor	an international boundary or the area (often fortified) immediately inside the boundary