astronomy vs selenology

astronomy and selenology both are nouns.

Word	Noun	Adjective	Verb	Adverb
astronomy	Yes	No	No	No
selenology	Yes	No	No	No

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

astronomy: the branch of physics that studies celestial bodies and the universe as a whole
selenology: the branch of astronomy that deals with the moon

astronomy (noun)	selenology (noun)
the branch of physics that studies celestial bodies and the universe as a whole	the branch of astronomy that deals with the moon