labium vs labia minora

labium and labia minora both are nouns.

Word	Noun	Adjective	Verb	Adverb
labium	Yes	No	No	No
labia minora	Yes	No	No	No

As nouns, labia minora is a hyponym of labium; that is, labia minora is a word with a more specific, narrower meaning than labium:

labium: a liplike structure that bounds a bodily orifice (especially any of the four labiate folds of a woman's vulva)
labia minora: the two inner folds of the vulva

Other hyponyms of labium include labia majora.

labium (noun)	labia minora (noun)
a liplike structure that bounds a bodily orifice (especially any of the four labiate folds of a woman's vulva)	the two inner folds of the vulva