demerit vs stigma

demerit and stigma both are nouns.

Word	Noun	Adjective	Verb	Adverb
demerit	Yes	No	No	No
stigma	Yes	No	No	No

As nouns, stigma is a hypernym of demerit; that is, stigma is a word with a broader meaning than demerit:

demerit: a mark against a person for misconduct or failure; usually given in school or armed forces
stigma: a symbol of disgrace or infamy

Other hypernyms of demerit include brand, mark, stain.

demerit (noun)	stigma (noun)
the quality of being inadequate or falling short of perfection	a skin lesion that is a diagnostic sign of some disease
a mark against a person for misconduct or failure; usually given in school or armed forces	an external tracheal aperture in a terrestrial arthropod
	a symbol of disgrace or infamy
	the apical end of the style where deposited pollen enters the pistil