cytology vs biology

cytology and biology both are nouns.

Word	Noun	Adjective	Verb	Adverb
cytology	Yes	No	No	No
biology	Yes	No	No	No

As nouns, biology is a hypernym of cytology; that is, biology is a word with a broader meaning than cytology:

cytology: the branch of biology that studies the structure and function of cells
biology: the science that studies living organisms

Other hypernyms of cytology include biological science, microscopic anatomy.

cytology (noun)	biology (noun)
the branch of biology that studies the structure and function of cells	the science that studies living organisms
	all the plant and animal life of a particular region
	characteristic life processes and phenomena of living organisms