Definition of sine qua non in English:

sine qua non

noun

  • An essential condition; a thing that is absolutely necessary.

    ‘grammar and usage are the sine qua non of language teaching and learning’
    • ‘Adopt these strategies for putting the sine qua non of job search success - networking - to the test.’
    • ‘This practice, one of the sine qua nons of Hungarian rural life, has lost much of its original sacral, ritual meaning.’
    • ‘There are three sine qua nons of guerilla warfare.’
    • ‘Clearly the first of two sine qua nons is to be able to express one calculated column in terms of another.’
    • ‘The study subjects obviously are the sine qua nons of a clinical trial.’

Origin

Latin, literally (cause) without which not.

Pronunciation:

sine qua non

/ˌsɪni kwɑː ˈnəʊn//ˌsʌɪni kweɪ ˈnɒn/