When a quantity is represented by a letter, it is called a literal factor to distinguish it from a numerical factor which is represented by a numeral. In the expression 8ab, 8 is a numerical factor, while a and b are literal factors.

A term is a group of values separated by addition or subtraction. A factor is a group of values separated by multiplication or division. For example: 2x+3y=12 In this case 2x is a term, and 3y is a term. In 2x, 2 is numerical, and x is a variable so 2 is the numerical factor. This is also called a coefficiant.