This unsmoked, wet-cured ham is the sine qua non of Parisian butcher shops: a light, ephemeral meat, sweet but umami.
That accumulation of identities is already a sine qua non when speaking of Hispanics, like Zimmerman.
In the land of the industrial revolution, foreign ownership and management is the sine qua non of industrial success.
"an indispensable condition," Latin, literally "without which not," from sine "without" (see sans) + qua ablative fem. singular of qui "which" (see who) + 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.
The essential, crucial, or indispensable ingredient without which something would be impossible: “Her leadership was the sine qua non of the organization's success.” From Latin, meaning “without which nothing.”