Assignment and assertion

Naturals = {1,2,3, ...} and Students = {JohnDoe, JaneBrown, ...} are assignments,

4 ÎA, 11 Ï A, and A = B are true assertions, 12 Î A is a false assertion.

Assignments and assertions are examples of well-formed expressions. 4 Î 4 is not a well-formed expression.

Note: Symbol = is overloaded since it is used for both assignment and assertion.