## Mathematical Analysis## Calculus Basics |

## What does the strange symbol “iff” mean in calculus? |

The symbol (or “word”) iff actually is shorthand for “if and only if.” It is not only mathematics that depends on the iff, but also philosophy, logic, and many technical fields. It is usually italicized; in addition, the phrase “P is necessary and sufficient for Q” is also seen as “Q iff P.” The corresponding logical symbols for “if and only if” are ↔ and ≡.