agate vs moss agate

agate and moss agate both are nouns.

Word	Noun	Adjective	Verb	Adverb
agate	Yes	No	No	No
moss agate	Yes	No	No	No

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

agate: an impure form of quartz consisting of banded chalcedony; used as a gemstone and for making mortars and pestles
moss agate: an agate resembling moss with brown, black, or green markings

agate (noun)	moss agate (noun)
an impure form of quartz consisting of banded chalcedony; used as a gemstone and for making mortars and pestles	an agate resembling moss with brown, black, or green markings