Variable, Expession, Value, Constant, and Numerical Coefficient.

Variable- A letter that represents an unknown number.
(Examples on side.)

Expression- Any single number, variable or combination of operations (+, -, and x.) involving numbers and variables.
(Examples on side.)

Value- A known or calculated amount.

Constant- A number that doesn't change and increases or decreases the value of the expression.

Numerical Coefficient- A number that multiplies the variable.