In set theory<span>, the </span>complement of a set A<span> refers to </span>elements<span> not in </span>A<span>. The </span>relative complement<span> of </span>A<span> with respect to a set </span>B<span>, written </span><span>B \ A</span><span>, is the set of elements in </span>B<span> but not in </span>A<span>. When all sets under consideration are considered to be </span>subsets<span> of a given set </span>U<span>, the </span>absolute complement<span> of </span>A<span> is the set of elements in </span>U<span> but not in </span>A<span>.
</span>The empty set<span> is the </span>set<span> containing no elements. In mathematics, and more specifically </span>set<span> theory, the </span>empty set<span> is the unique </span>set<span> having no elements; its size or cardinality (count of elements in a </span>set<span>) is zero. </span> Roster Form<span>: 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. </span> Set-Builder Notation<span>. A shorthand used to write </span>sets<span>, often </span>sets<span> with an infinite number of elements. Note: The </span>set<span> {x : x > 0} is read aloud, "the </span>set<span> 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. </span> Universal set:<span>the set containing all objects or elements and of which all other sets are subsets.</span>
