What is  Doublet?

Doublet is the name of the popular word puzzle invented by Lewis Carroll - now also known by a variety of other names: Word Ladders, Ladderwords, Stepwords, Word Chains, Laddergrams, Transitions, Transformations, etc.

Transform one word into another by changing a single letter in each step, so that each link in the chain is a valid word. For example, to change MORE into LESS with 3 links: