terpene vs limonene

terpene and limonene both are nouns.

Word	Noun	Adjective	Verb	Adverb
terpene	Yes	No	No	No
limonene	Yes	No	No	No

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

terpene: an unsaturated hydrocarbon obtained from plants
limonene: a liquid terpene with a lemon odor; found in lemons and oranges and other essential oils

Other hyponyms of terpene include terpinene.

terpene (noun)	limonene (noun)
an unsaturated hydrocarbon obtained from plants	a liquid terpene with a lemon odor; found in lemons and oranges and other essential oils