si ‧ ne qua non /ˌsɪni kwɑː ˈnəʊn $ -ˈnɑːn/ BrE AmE noun [singular] formal
[ Date: 1600-1700 ; Language: Late Latin ; Origin: 'without which not' ]
something that you must have, or which must exist, before something else can happen SYN prerequisite
sine qua non for/of
The control of inflation is a sine qua non for economic stability.