milk glass vs opal glass

milk glass and opal glass both are nouns.

Word	Noun	Adjective	Verb	Adverb
milk glass	Yes	No	No	No
opal glass	Yes	No	No	No

As nouns, milk glass and opal glass are synonyms defined as:

milk glass (noun)	opal glass (noun)
a milky white translucent or opaque glass	a milky white translucent or opaque glass