Tag: element

In mathematics, an element, or member, of a set is any one of the distinct objects that make up that set.
Writing A = {1, 2, 3, 4 } means that the elements of the set A are the numbers 1, 2, 3 and 4. Sets of elements of A, for example {1, 2}, are subsets of A.
Sets can themselves be elements. For example consider the set B = {1, 2, {3, 4}}. The elements of B are not 1, 2, 3, and 4. Rather, there are only three elements of B, namely the numbers 1 and 2, and the set {3, 4}.
The elements of a set can be anything. For example, C = { red, green, blue }, is the set whose elements are the colors red, green and blue.
The relation “is an element of”, also called set membership, is denoted by ∈. Writing
means that “x is an element of A”. Equivalent expressions are “x is a member of A”, “x belongs to A”, ” is in A” and “x lies in A”. The expressions “A includes x” and “A contains x” are also used to mean set membership, however some authors use them to mean instead “x is a subset of A”. Logician…