penance vs sacrament

penance and sacrament both are nouns.

Word	Noun	Adjective	Verb	Adverb
penance	Yes	No	No	No
sacrament	Yes	No	No	No

As nouns, sacrament is a hypernym of penance; that is, sacrament is a word with a broader meaning than penance:

penance: a Catholic sacrament; repentance and confession and atonement and absolution
sacrament: a formal religious ceremony conferring a specific grace on those who receive it; the two Protestant ceremonies are baptism and the Lord's Supper; in the Roman Catholic Church and the Eastern Orthodox Church there are seven traditional rites accepted as instituted by Jesus: baptism and confirmation and Holy Eucharist and penance and holy orders and matrimony and extreme unction

penance (noun)	sacrament (noun)
voluntary self-punishment in order to atone for some wrongdoing	a formal religious ceremony conferring a specific grace on those who receive it; the two Protestant ceremonies are baptism and the Lord's Supper; in the Roman Catholic Church and the Eastern Orthodox Church there are seven traditional rites accepted as instituted by Jesus: baptism and confirmation and Holy Eucharist and penance and holy orders and matrimony and extreme unction
a Catholic sacrament; repentance and confession and atonement and absolution
remorse for your past conduct