penitent (adj.)

"sorry for offenses committed, repentant of one's sins, contrite," mid-14c., from Old French pénitent (14c.) and directly from Latin paenitentem (Medieval Latin penitentem) "penitent" (see penitence).

As a noun, "one undergoing penance, a repentant sinner," late 14c., from the adjective (earlier in this sense was penaunt, early 14c., from Old French peneant). Also, in plural, a name distinguishing some Catholic orders, especially those formed for the reception of reformed courtesans.

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Definitions of penitent from WordNet
penitent (n.)
(Roman Catholic Church) a person who repents for wrongdoing (a Roman Catholic may be admitted to penance under the direction of a confessor);
penitent (adj.)
feeling or expressing remorse for misdeeds;
Synonyms: repentant