Mannheim distance

Mannheim distance is like a way of measuring how far away two words are from each other. It counts how many changes you need to make to a word to turn it into another word. For example, if you want to change the word 'cat' to the word 'dog', you need to change three letters (c to d, a to o and t to g). So the Mannheim distance between 'cat' and 'dog' is 3.