# Definition of Successor and Predecessor in Math

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In math, the terms successor and predecessor refer to the numbers directly after or directly before a given number, respectively. To find the successor of a given whole number, add one to the given number. To find the predecessor of a given whole number, subtract one from the given number.

## Examples

Suppose that the given number is 18. Its successor is 19, and its predecessor is 17. If the given number were 226, it would have a successor of 227 and a predecessor of 225. Additionally, if x is the successor of y, then y is the predecessor of x. For instance, 80 is the successor of 79, so therefore 79 is the predecessor of 80.

## Whole Numbers

The terms successor and predecessor apply only to whole numbers—that is, zero, one, two, three and so on; they do not apply to fractions, decimals or negative numbers. Every whole number has a successor. With the exception of zero, every whole number also has a predecessor.