Variable: A letter that represents an unknown number.
Example: x, a, n, y, etc.
Expression: Any single number or variable, or combination of operations involving numbers and variables.
Example: 5, n, 8, 8t, x + 1, 2y - 7
Note: There are no equal signs (=) in an expression.
Value: A known or calculated amount.
Numerical Coefficient: A number that multiplies the variable.
("2" is the numerical coefficient, "t" is the variable.)