What is the number left after dividing one whole number by another called?

When one whole number is divided by another, the result can be described in specific terms related to division. The term 'remainder' refers to the amount left over after the division process is completed when the numbers do not divide evenly. For example, if you have 10 divided by 3, the quotient is 3, because 3 goes into 10 three times (which equals 9), and then there is 1 left over. That leftover amount, which in this case is 1, is known as the remainder.

In contrast, the other terms—quotient, dividend, and factor—have different meanings. The quotient is the result of the division itself, the dividend is the number being divided, and a factor is a number that can be multiplied by another to yield a specific number. Thus, in the context of the question, 'remainder' accurately identifies the leftover portion after the division, making it the correct answer.