cupule vs acorn cup

cupule and acorn cup both are nouns.

Word	Noun	Adjective	Verb	Adverb
cupule	Yes	No	No	No
acorn cup	Yes	No	No	No

As nouns, cupule and acorn cup are synonyms defined as:

cupule and acorn cup: cup-shaped structure of hardened bracts at the base of an acorn

cupule (noun)	acorn cup (noun)
a sucker on the feet of certain flies	cup-shaped structure of hardened bracts at the base of an acorn
cup-shaped structure of hardened bracts at the base of an acorn