The intersection of two sets refers to the set of elements that are common to both sets. It is denoted by the symbol ∩. If two sets have shared elements, their intersection forms a new set with just those common values.
\[ A \cap B = \{x \mid x \in A \text{ and } x \in B\} \]
This means the set of all elements x such that x is in both set A and set B.
Let:
\[ A = \{2, 3, 4, 5\}, \quad B = \{3, 5, 7, 9\} \] \[ A \cap B = \{3, 5\} \]