Blog · 2026-09-25

What is a word ladder? The 150-year-old puzzle behind Poople

A word ladder is a puzzle where you turn one word into another by changing a single letter at a time, and every rung of the ladder has to be a real word. Turn COLD into WARM: COLD → CORD → CARD → WARD → WARM. Four changes, four real words in between.

Where it came from

Lewis Carroll, the author of Alice in Wonderland, came up with the idea on Christmas Day 1877 and published it in Vanity Fair in 1879 under the name "Doublets". His readers sent in ladders like HEAD → HEAL → TEAL → TELL → TALL → TAIL, and the puzzle has been in newspapers and puzzle books ever since. Computer scientists later adopted it as a classic exercise in graph search: every word is a node, every one-letter change is an edge, and the shortest ladder is a shortest path.

Why four letters

Three-letter words are so densely connected that almost everything is two or three steps apart, which makes the puzzle trivial. Five-letter words are sparse: many of them have no neighbours at all, so ladders get long or impossible. Four-letter English words sit in the middle. A word list of a couple of thousand words gives most words a handful of neighbours, ladders of three to seven steps, and enough dead ends to make you think.

How Poople uses it

Poople fixes the goal word: every ladder ends at POOP. That changes the game in a nice way. Because the target never moves, you learn the map. Words like LOOP, HOOP, COOP, POOL, POOR and PROP are one step from the end, so the real puzzle is steering from a random starting word toward one of those gateways in as few moves as possible. A new starting word every day keeps it fresh; the fixed goal makes you better over time.

Want to try one now? Play today's Poople Unlimited, or use the solver to see the shortest ladder between any two words.