In a subtraction problem it is useful to have names for the various parts. In a - b the entire expression is called a "difference," and the answer to a - b is the difference, or occasionally the "remainder." These two terms arise from two ways in which subtraction is used in practical problems. The first number, a, is called the "minuend." This is the part that is diminished or made smaller when something is subtracted from it (provided that that something is positive). The second number, b, is the "subtrahend" or the part subtracted.