brain sugar vs sucrose

brain sugar and sucrose both are nouns.

Word	Noun	Adjective	Verb	Adverb
brain sugar	Yes	No	No	No
sucrose	Yes	No	No	No

As nouns, sucrose is a hypernym of brain sugar; that is, sucrose is a word with a broader meaning than brain sugar:

brain sugar: a simple sugar found in lactose
sucrose: a complex carbohydrate found in many plants and used as a sweetening agent

Other hypernyms of brain sugar include saccharose.

brain sugar (noun)	sucrose (noun)
a simple sugar found in lactose	a complex carbohydrate found in many plants and used as a sweetening agent