residue vs remnant

residue and remnant both are nouns.

Word	Noun	Adjective	Verb	Adverb
residue	Yes	No	No	No
remnant	Yes	No	No	No

As nouns, remnant is a hyponym of residue; that is, remnant is a word with a more specific, narrower meaning than residue:

residue: something left after other parts have been taken away
remnant: a small part or portion that remains after the main part no longer exists

Other hyponyms of residue include leftover.

residue (noun)	remnant (noun)
something left after other parts have been taken away	a piece of cloth that is left over after the rest has been used or sold
matter that remains after something has been removed	a small part or portion that remains after the main part no longer exists