imperfection (n.)

late 14c., "incompleteness, deficiency, lack," from Old French imperfeccion "defect; imperfect state" (12c.) and directly from Late Latin imperfectionem (nominative imperfectio) "imperfection," noun of action from Latin imperfectus "imperfect"(see imperfect). Meaning "an instance of being imperfect" is from early 15c.