Cartesian Product: For a given sequence of sets X1, .. ,Xn the sequences of elements of these sets that satisfy them simultaneously. In something close to the standard notation of set theory: { (x1, .. ,xn): (x1, .. ,xn) e (X1, .. ,Xn) }
This may be read as "the sequences made up of respectively x1 .. xn that are element of the sequence of sets of respectively X1 .. Xn (with x1 an element of X1, x2 of X2 and so on)". This is a very powerful idea from set theory that helps to analyse and explain anything whatsoever that is structurally complex.
