- of his, her, its, or their own kind; unique.
Word Origin and History for sui generis
1787, Latin, literally "of one's own kind, peculiar." First element from sui, genitive of suus "his, her, its, one's," from Old Latin sovos, from PIE root *swe-, pronoun of the third person (see idiom).
A person or thing that is unique, in a class by itself: “She is an original artist; each of her paintings is sui generis.” From Latin, meaning “of its own kind.”