An equation consists of an algebraic expression (or just a variable), optionally followed by an equals "=" sign and another algebraic expression. For example, "a + b = c^2" is an equation relating a, b, and c. If just one expression is given, "= 0" is assumed. For example, the equations "a + b = 2" and "a + b - 2" mean the same thing.

Constant expressions are valid in equations. A constant expression is an algebraic expression involving numbers, operators, built-in functions and built-in constants (like pi).