Foundations of Mathematics

Set Theory

What is a null or empty set?

A null or empty set contains no elements; an empty set is considered to be a subset of every other set. The opposite of an empty set is, logically, a nonempty set, or one that is not empty. The notations for empty set are { } and ∅, but not ( ), as it is sometimes written in texts. Interestingly enough, an empty set is considered to be both open and closed for any set X.


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