Guys you don't need 10 posts in the same thread explaining the same thing. If you see that someone has already answered ( especially when there are 10 of them ) there's no point posting the same shit again. It's just spam.
Though actually there are two quite different definitions being proposed here:
1. Return ON Investment - the classical definition, and in my view the correct one, in other words,
how much will I get back for a given investment (in a defined timescale)
vs
2. Return OF Investment - widely used here to mean
will I get back the money I invest, and (by implication)
when?