amount left over after dividing one integer by another From Wikipedia, the free encyclopedia

In arithmetic, the result of the division of two integers usually cannot be expressed with an integer quotient, unless a **remainder—**an amount "left over" after the division—is also accepted.

Given a natural number and a non-zero natural number , it can be shown that there exist unique integers and , such that and . The number is called the *quotient*, while is called the *remainder*.^{[1]}^{[2]}

If and are integers with being non-zero, then a remainder is an integer such that for some integer , and with .

When defined this way, there are two possible remainders. For example, the division of -42 by -5 can be expressed as either

or

- .

So the remainder is then either 3 or -2.

This ambiguity in the value of the remainder is not very serious; in the case above, the negative remainder is obtained from the positive one just by subtracting 5, which is . This holds in general. When dividing by , if the positive remainder is , and the negative one is , then

- .

When and are real numbers, with being non-zero, then can be divided by without remainder, with the quotient being another real number. If the quotient is constrained to being an integer, however, the concept of remainder is still necessary. It can be proven that there exists a unique integer quotient and a unique real remainder such that with . Similar to the case of division of integers, the remainder could be required to be negative, that is, .

Extending the definition of remainder for real numbers, as described above, is not of theoretical importance in mathematics; however, many programming languages implement this definition—see modulation for more.

- Divisor, a number which evenly divides another
- Long division
- Modular arithmetic
- Modulation

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