loaf sugar vs refined sugar

loaf sugar and refined sugar both are nouns.

Word	Noun	Adjective	Verb	Adverb
loaf sugar	Yes	No	No	No
refined sugar	Yes	No	No	No

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

loaf sugar: a large conical loaf of concentrated refined sugar
refined sugar: a white crystalline carbohydrate used as a sweetener and preservative

Other hypernyms of loaf sugar include loaf, sugar.

loaf sugar (noun)	refined sugar (noun)
a large conical loaf of concentrated refined sugar	a white crystalline carbohydrate used as a sweetener and preservative