Yep, it's yet another rule of inference used in propositional logic. It is written as Imp or Impl for short.
(P→Q) = (¬P∨Q)
(P therefor Q) = (either 'not P' or Q)
Or in English:
If it rains (P), then I'll get wet (Q).
is the same as...
Either it won't rain (~P), or I'll get wet (Q).
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