What Does X X Mean in Sets

147. Glossary of mathematical notation and terminology. Set membership x ∈ X means x is an element of the set X. (Non-membership is written x ∈ X.) Set inclusion X ⊆ Y means every element of X is an element of Y ; X is a subset of Y .

What does X X means in set?

147. Glossary of mathematical notation and terminology. Set membership x ∈ X means x is an element of the set X. (Non-membership is written x ∈ X.) Set inclusion X ⊆ Y means every element of X is an element of Y ; X is a subset of Y .

What does 2 X's mean in math?

When you see the notation 2X, where X is a set, we’re also considering 2 as a set, in fact 2={0,1}. So 2X is the collection of all functions mapping X to {0,1}. It’s been stated in a comment that 2X is the power set of X, that is, the collection of all subsets of X.