Relating to or descended from relatives on the mother's side of the family, or related by blood through either parent.
From Latin cognatus (born together, related) combining cum- (with) and gnatus (born), plus the suffix -ical. The word originally referred to kinship relationships in Roman law and evolved to describe family relationships generally.
Ancient Romans distinguished between agnate (relatives through your father) and cognate (relatives through your mother), which shaped their entire legal system for inheritance and citizenship—a word's structure literally encoded their social rules!
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