cover glass vs plate glass

cover glass and plate glass both are nouns.

Word	Noun	Adjective	Verb	Adverb
cover glass	Yes	No	No	No
plate glass	Yes	No	No	No

As nouns, plate glass is a hypernym of cover glass; that is, plate glass is a word with a broader meaning than cover glass:

cover glass: a small and very thin piece of glass used to cover the specimen on a microscope slide
plate glass: glass formed into large thin sheets

Other hypernyms of cover glass include sheet glass.

cover glass (noun)	plate glass (noun)
a small and very thin piece of glass used to cover the specimen on a microscope slide	glass formed into large thin sheets