In a word ladder, a start and an end word are provided, and the solution consists of the steps or rungs between the words. Each step is itself a common, non-capitalized word, formed by changing the previous word according to a set of rules. Plurals and other forms of words are acceptable. There are several possible rule sets for changing words.
A Lewis Carroll word ladder is named for its inventor. To change each rung of the ladder, one can add a letter, remove a letter, change a letter, or anagram the word.
Example: From GO to STOP (3 rungs)
1. GOT (added a letter)
2. POT (changed a letter)
3. POTS (added a letter)
In a constricted word ladder, the only legal change is to change a letter of the word.
Example: From EASY to HARD (4 rungs)
Example taken from Wikipedia
Although technically these are open solution puzzles, since there may be more than one series of rungs, ordinarily there is a single solution. If you find a solution with fewer rungs than specified, you will get an additional win point for beating the puzzle-maker.