Propositional Logic: A if and only if B

This video shows how to evaluate conditional statements of the form "A if and only if B", or "A iff B". These are also called "biconditionals".

[markganus]

I found the triangle example particularly useful. spot on

[garyhughes]

Confused until I watched this video. Now it all makes sense. In a biconditional A=B and B=A. But without the ‘only if’ condition, A implies B, but B does not necessarily imply A. I think I’d be right in saying that in the first case, where A and B are equivalent, then both A and B are ‘sufficient conditions’ for each other. But where A only implies B, then this wouldn’t be the case. Still confused, but feel I’m getting there.