art vs horology

art and horology both are nouns.

Word	Noun	Adjective	Verb	Adverb
art	Yes	No	No	No
horology	Yes	No	No	No

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

art: a superior skill that you can learn by study and practice and observation
horology: the art of designing and making clocks

art (noun)	horology (noun)
the creation of beautiful or significant things	the art of designing and making clocks
the products of human creativity; works of art collectively
a superior skill that you can learn by study and practice and observation
photographs or other visual representations in a printed publication