swap

Also known as "swap space." When a program requires more memory than is physically available in the computer, currently-unused information can be written to a temporary buffer on the hard disk, called swap, thereby freeing memory. Some operating systems support swapping to a specific file, but Linux normally swaps to a dedicated swap partition. A misnomer, the term swap in Linux is used to define demand paging.

Swap partitions are often set at least equal to the amount of available memory up to certain limits.