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
Phobos	FO-bos (English)	Greek Mythology
Silvia	SEEL-vyah (Italian), SEEL-byah (Spanish)	Italian, Spanish, Portuguese, Romanian, Slovak, English, German, Late Roman, Roman Mythology
Dorte	DOR-te	Danish
Wynonna	wi-NON-ə	English (Rare)
Destiny	DES-tə-nee	English
Shadya	-	Arabic