# Are math definitions iff statements? [duplicate]

I was wondering if definitions in mathematics are "if and only" statements?

I know for sure that theorems are not "iff" statements.

Thank you in advance for your help.

• Yes, they are. But usually only "if" is used. Dec 11, 2015 at 15:46

## 1 Answer

Yes, any definition is a 'iff' statement, though we use just 'if' in definition.