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
