In mathematics, a set is a collection of distinct objects. Each object, or element, can occur at most once. Ordering is not significant: sets do not impose any ordering on their elements.
Sets are usually named using capital letters, and brackets, {}, are used to enumerate a set’s elements. For example:
Two sets are considered equal if and only if they contain exactly the same elements.
Symbols:
denotes set membership. i.e.,
. We can say that
is a member of
or
belongs to
. We can also say that
contains
.
means that an element is not a member of a set.
Sets may be finite or infinite. is an example of an infinite set.