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⊂B.
For example, if A is the set {♢,♡,♣,♠} and B is the set {♢,△,♡,♣,♠}, then A⊂B but B⊄A. Since B contains elements not in A, we can say that A is a proper subset of B. Or if I1 is the interval [0,2] and I2 is the interval [0,1], then I2⊂I1.
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