watch crystal vs watch glass

watch crystal and watch glass both are nouns.

Word	Noun	Adjective	Verb	Adverb
watch crystal	Yes	No	No	No
watch glass	Yes	No	No	No

As nouns, watch crystal and watch glass are synonyms defined as:

watch crystal and watch glass: a protective cover that protects the face of a watch

Other synonyms of watch crystal include crystal.

watch crystal (noun)	watch glass (noun)
a protective cover that protects the face of a watch	a protective cover that protects the face of a watch
	laboratory glassware; a shallow glass dish used as an evaporating surface or to cover a beaker