Relationship between two propositional forms P and Q, noted as “P ↔ Q” or “P

*is equal to*Q”, which is true when P and Q both simultaneously have the same truth value and false in other cases.Synonym for

**.***biconditional propositional form*The biconditional truth table is:

P | Q | P ↔ Q |

T | T | T |

T | F | F |

F | T | F |

F | F | T |

### Example

An equation is a propositional form.

2*x* + 8*y* = 16 ↔ *x* + 4*y* = 8

This expression is a biconditional propositional form that can also be translated by: *we can multiply or divide all the terms in an equation by a non-zero number without changing its truth value.*.