Writing means that the elements of the set A are the numbers 1, 2, 3 and 4. Sets of elements of A, for example , are subsets
Sets … See more

The relation "is an element of", also called set membership, is denoted by the symbol "∈". Writing
means that "x is an element of A". Equivalent expressions are "x is a member of A", "x bel… See more

Using the sets defined above, namely A = {1, 2, 3, 4}, B = {1, 2, {3, 4}} and C = {red, green, blue}, the following statements are true:
• 2 ∈ A
• 5 ∉ A… See more

The number of elements in a particular set is a property known as cardinality; informally, this is the size of a set. In the above examples, the cardinality of the set A is 4, while the cardinality of set B and set C are both 3. … See more

As a relation, set membership must have a domain and a range. Conventionally the domain is called the universe denoted U. The range is the set of subsets of U called the power set of U and denoted P(U). Thus the relation is … See more

• Identity element
• Singleton (mathematics) See more