Jaro-Winkler Distance

The Jaro-Winkler distance is a measure of dissimilarity between two strings that gives additional weight to a common prefix. For strings and , let be the number of matching characters within the matching window, and let be half the number of out-of-order matches. When , the Jaro similarity is

(1)

The matching window has radius . If , then .

If is the length of the common prefix, usually capped at 4, and is a prefix scaling factor, usually , then when exceeds a similarity threshold, usually , the Jaro-Winkler similarity is

(2)

Otherwise, . The associated distance is

(3)

With the usual choices and , it lies between 0 and 1, with 0 indicating identical strings. Despite its name, it does not in general satisfy the triangle inequality.