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iff
if and only if
Biconditional

A way of writing two conditionals at once: both a conditional and its converse.

For example, the statement "A triangle is equilateral iff its angles all measure 60°" means both "If a triangle is equilateral then its angles all measure 60°" and "If all the angles of a triangle measure 60° then the triangle is equilateral".

Biconditionals can be written using the ⇔ symbol:

A triangle is equilateral ⇔ its angles all measure 60°

 

See also

Inverse, contrapositive

 


  this page updated 27-aug-12
Mathwords: Terms and Formulas from Algebra I to Calculus
written, illustrated, and webmastered by Bruce Simmons
NCTM Web Bytes December 2004 Web Bytes March 2005 Web Bytes