Words related to non-
sine qua non
"an indispensable condition," Latin, literally "without which not," from sine "without" (see sans) + qua ablative fem. singular of qui "which" (from PIE root *kwo-, stem of relative and interrogative pronouns) + non "not" (see non-). Feminine to agree with implied causa. The Latin phrase is common in Scholastic use. Sometimes a masculine form, sine quo non, is used when a person is intended. Proper plural is sine quibus non.
mid-14c., noumper, from Old French nonper "odd number, not even," in reference to a third person to arbitrate between two, from non "not" (see non-) + per "equal," from Latin par "equal" (see par (n.)). Initial -n- lost by mid-15c. due to faulty separation of a noumpere, heard as an oumpere. Originally legal, the gaming sense first recorded 1714 (in wrestling).