An edit operation is the insertion, deletion, or substitution of a single symbol from a string. Edit operations are applied to genetic strings to model small-scale mutations.

When insertions or deletions of symbols appear consecutively, then the resulting contiguous interval is called a gap.

Finding the minimum number of edit operations possible required to transform a string $s$ into another string $t$ yields the edit distance $d_{\textrm{Edit}}(s, t)$.