Propositions that have the same truth value.

Synonym for identity.

### Symbol

The equivalence of the two propositions P and Q is noted as: P \(\iff\) Q and is read as: “P is equivalent to Q” or “P if and only if Q”.

### Examples

- For the real values of
*x*, the following propositions are equivalent:

4*x*+ 2 = 12 \(\iff\)*x*= 2.5. - “The triangles ABC and DEF are similar” \(\iff\) “The corresponding angles of triangles ABC and DEF are isometric”.