The word "ascertain" is a verb. It means to find out something with certainty.
It's an adjective. It describes something that can happen but it is not a certainty.
part of speech
The part of speech for this particular word is a noun.
adverb
what part of speech is beneath
The part of speech for "answer" is a noun.
The part of speech for "explicit" is an adjective.
The part of speech for "unfamiliar" is an adjective.
The part of speech for "indefinite" is an adjective.
The part of speech for "lecturer" is a noun.
The part of speech for "breezy" is an adjective.