Mathematical texts commonly denote sets by capital letters in italic, such as A, B, C. A set may also be called a collection or family, especially … See more

A singleton set is a set with exactly one element; such a set may also be called a unit set. Any such set can be written as {x}, where x is the element. The set {x} and the element x … See more

An Euler diagram is a graphical representation of a collection of sets; each set is depicted as a planar region enclosed by a loop, with its … See more

If B is a set and x is an element of B, this is written in shorthand as x ∈ B, which can also be read as "x belongs to B", or "x is in B". The statement "y is not an element of B" is written as y ∉ … See more

The empty set (or null set) is the unique set that has no members. It is denoted ∅, $${\displaystyle \emptyset }$$, { }, ϕ, or ϕ. See more

If every element of set A is also in B, then A is described as being a subset of B, or contained in B, written A ⊆ B, or B ⊇ A. The latter notation … See more

There are sets of such mathematical importance, to which mathematicians refer so frequently, that they have acquired special names and notational conventions to identify them. See more