We can write a set either by listing its elements or describing the set. Consider the set of prime numbers less than 20 to be denoted as A, therefore we can represent the set A as A= (2, 3, 5, 7, 11, 13, 17, 19), A= (x/x is a prime number less than 20). I mathematics, we demote a set by upper case letters while its elements by lower case letters. For example, the set of natural numbers is denoted by N.

Subset

For a set to be a subset of another set, it implies that all its elements are all found in the other set. A subset is denoted by the symbol;

Ϲ  = subset of

Ȼ = not a subset of

For example; if A= (1, 2, 3, 4, 5, 6, 7) and B= (1, 2, 3) then B C A.

N.B. every set is a subset of itself. Symbols used in identifying a set include;