In set theory, the complement of a set A refers to elements not in A. The relative complement of A with respect to a set B, written B \ A, is the set of elements in B but not in A. When all sets under consideration are considered to be subsets of a given set U, the absolute complement of A is the set of elements in U but not in A.
The empty set is the set containing no elements. In mathematics, and more specifically set theory, the empty set is the unique set having no elements; its size or cardinality (count of elements in a set) is zero.
Roster Form: This method is also known as tabular method. In this method, a set is represented by listing all the elements of the set, the elements being separated by commas and are enclosed within flower brackets { }. Example: A is a set of natural numbers which are less than 6.
Set-Builder Notation. A shorthand used to write sets, often sets with an infinite number of elements. Note: The set {x : x > 0} is read aloud, "the set of all x such that x is greater than 0." It is read aloud exactly the same way when the colon : is replaced by the vertical line.
Universal set:the set containing all objects or elements and of which all other sets are subsets.