a sine qua non

(formal)

something that is necessary, especially if you are going to achieve a particular thing (often + of ) The company sees training as the sine qua non of success.

Common Names:

Name	Pronounced	Usage
EstefÂNia	-	Portuguese
Passang	-	Tibetan, Bhutanese
RÉGine	-	French
Gerarda	je-RAHR-dah (Italian)	Italian, Dutch
Rajendra	-	Indian, Hindi, Marathi, Gujarati, Telugu, Nepali
Phyllis	FIL-is (English)	Greek Mythology, English, German