Let X and Y be random variables, F be a function. I have seen in a variety of contexts that they write "E(X) < ∞". What does it mean? My guess is that it means that E(X) is finite, but if this is the case, shouldn't they say -∞ < E(X) < ∞ instead? Also, I have seen the notation of the letter "d" above the equal sign. What does it mean? e.g. d X=F(Y) [the "d" should be above the equal sign, not above X] Does anyone have any idea or have seen the above notation? Thanks for any help!