bitter orange vs Citrus aurantium

bitter orange and Citrus aurantium both are nouns.

Word	Noun	Adjective	Verb	Adverb
bitter orange	Yes	No	No	No
Citrus aurantium	Yes	No	No	No

As nouns, bitter orange and Citrus aurantium are synonyms defined as:

bitter orange and Citrus aurantium: any of various common orange trees yielding sour or bitter fruit; used as grafting stock

Other synonyms of bitter orange include bigarade, bitter orange tree, marmalade orange, Seville orange, sour orange.

bitter orange (noun)	Citrus aurantium (noun)
highly acidic orange used especially in marmalade	any of various common orange trees yielding sour or bitter fruit; used as grafting stock
any of various common orange trees yielding sour or bitter fruit; used as grafting stock