mouthless vs biological science

mouthless is not a noun while biological science is a noun.

Word	Noun	Adjective	Verb	Adverb
mouthless	No	Yes	No	No
biological science	Yes	No	No	No

mouthless (noun)	biological science (noun)
	the science that studies living organisms

mouthless (adjective)	biological science (adjective)
having no mouth or mouthlike opening