sine qua non
noun /ˌsɪneɪ kwɑː ˈnəʊn/
  /ˌsɪneɪ kwɑː ˈnəʊn/
 [singular] (from Latin, formal)- sine qua non (of/for something) something that is essential before you can achieve something else必要条件 - TV coverage is the sine qua non of a sport if it is to thrive.电视报道是一项运动蓬勃发展的必要条件。 
- Trust is a sine qua non for any counselling.信任是任何咨询的必要条件。 
 词源Latin, literally ‘(cause) without which not’.
- TV coverage is the sine qua non of a sport if it is to thrive.