# Math Insight

### Definition of subset

A set A is a subset of another set B if all elements of the set A are elements of the set B. In other words, the set A is contained inside the set B. The subset relationship is denoted as A \subset B.

For example, if A is the set \{ \diamondsuit, \heartsuit, \clubsuit, \spadesuit \} and B is the set \{ \diamondsuit, \triangle, \heartsuit, \clubsuit, \spadesuit \}, then A \subset B but B \not\subset A. Since B contains elements not in A, we can say that A is a proper subset of B. Or if I_1 is the interval [0,2] and I_2 is the interval [0,1], then I_2 \subset I_1.