Originally Posted by Yorick

Wow... well, how's this: I create hypothetical scenarios all the time to illustrate a point. To preface my use of hypothesis, I'd say "let's hypothetically say that.... blah blah blah". I've even used the term numerous times on IW.

I am far from unusual in this regard, and know plenty of people that do. The scientific community are hardly unique in their use of English.

As for theory, that's a widely used word: A theory in how a crime was committed. Music theory. Economic theory. It's a very common word.

A theory contains hypothesis, but has more implied factuality. It is still a kind of hypothesis nonetheless: an imagined scenario with the intent of explaining or communicating something unproven or as yet unverified. Both are conjecture, as is a guess.

So the three words, while holding differences in preciseness or emphasis, do have related meanings and are synonymous with each other.