If and only if

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Revision as of 11:15, 7 December 2009

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-In [[logic]], the phrase '''if and only if''' means "is logically equivalent to", or "is a [[necessary]] and [[sufficient]] condition for". It is often abbreviated '''iff'''.
+#REDIRECT [[Implication]] [[Category:Logic]]
-For any statements '''P''' and '''Q''',
-: '''P''' if and only if '''Q'''
-means the same thing as:
-: '''P''' [[implies]] '''Q''', and '''Q''' implies '''P'''.
-[[Category:Logic]]