banana oil vs ester

banana oil and ester both are nouns.

Word	Noun	Adjective	Verb	Adverb
banana oil	Yes	No	No	No
ester	Yes	No	No	No

As nouns, ester is a hypernym of banana oil; that is, ester is a word with a broader meaning than banana oil:

banana oil: a liquid ester derived from amyl alcohol; has the odor of bananas
ester: organic compound formed by reaction between an acid and an alcohol with elimination of water

banana oil (noun)	ester (noun)
a liquid ester derived from amyl alcohol; has the odor of bananas	organic compound formed by reaction between an acid and an alcohol with elimination of water