Subsets, Universal Sets, Null Sets and Cardinality of Sets

Grade 7 Mathematics

1. The universal set U is the set that contains all objects under consideration.
2. Given any two sets A and B, if every element in A is also an element in B, then A is a subset of B. The symbol “A ⊆ B” is read A is a subset of B.
3. A set with no element is an empty set or null set. The symbol for empty set is { } or ∅.
4. The cardinal number of set A, denoted by n(A), is the number of elements in set A.

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