sebum vs smegma

sebum and smegma both are nouns.

Word	Noun	Adjective	Verb	Adverb
sebum	Yes	No	No	No
smegma	Yes	No	No	No

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

sebum: the oily secretion of the sebaceous glands; with perspiration it moistens and protects the skin
smegma: a white secretion of the sebaceous glands of the foreskin

sebum (noun)	smegma (noun)
the oily secretion of the sebaceous glands; with perspiration it moistens and protects the skin	a white secretion of the sebaceous glands of the foreskin