In information theory, the Hamming distance between two strings of equal length is the number of positions at which the corresponding symbols are different. In another way, it measures the minimum number of substitutions required to change one string into the other, or the minimum number of errors that could have transformed one string into the other. A major application is in coding theory, more specifically to block codes, in which the equal-length strings are vectors over a finite field . The Hamming distance between: On a two-dimensional grid such as a chessboard, the Hamming distance is the minimum number of moves it would take a rook to move from one cell to the other. For a fixed length n, the Hamming distance is a metric on the vector space of the words of length n (also known as a Hamming space ), as it fulfills the conditions of non-negativity, identity of indiscernibles and symmetry, and it can be shown by complete induction that it satisfies the triangle inequality as well. The Hamming distance between two words a and b can also be seen as the Hamming weight of a b for an appropriate choice of the operator. [ clarification needed ] https://en.wikipedia.org/wiki/Hamming_distance