sinecua is incorrectly written and should be written as "sine qua non" to be its meaning:The full expression is sine qua non or condition sine qua non, Latinism used primarily in the legal field, which means a condition without which, so it doesn't mean that things that we talk about is sufficient and necessary condition will be fulfilled following. It is the same condition that is expressed in the connective biconditional in propositional logic with " if and only if ". If and only if A is condition of B and B is A condition, then A is equal to B, i.e. is a sine qua non condition A to B and B condition, so that A and B are equal.
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