Most Word Ways readers are familiar with word ladders in which one changes letters one at a time, as CART-CARE-CORE-BORE-BONE. Such ladders can be embedded in word networks, first discussed in the May and August 1973 issues of Word Ways. In particular, one can define the distance between two words in a network as the number of steps in the minimum-length ladder joining these words, and the span of the network as the maximum distance taken over all possible pairs of words in the network.
Gordon, Leonard and Eckler, A. Ross
Word Ways: Vol. 29
, Article 2.
Available at: http://digitalcommons.butler.edu/wordways/vol29/iss2/2