Dictionary
cau•sa si•ne qua non
Pronunciation: (kou'sä si'ne kwä nōn'; Eng. kô'zu sī'nē kwā non', kô'zu sin'ā kwä nōn'), [key] Latin.
an indispensable condition; requisite.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.