B: Draws Cab

There are plenty of words which turn into other words when spelled backward. (No, not when spelled "backward," smart-aleck. When the order of the letters is reversed, okay?) "Straw" turns into "warts," "mart" into "tram," "room" into "moor," "reward" into "drawer." More unusual—or at least less commonly discussed—are words I call "switchbacks": words which turn into other words if you change one letter (to any other letter) and then reverse the order of the letters.

For instance:

  • elf <—> fly
  • bird <—> drab
  • deal <—> land
  • door <—> road
  • flaw <—> waif (or wolf)
  • liar <—> rain

As with ordinary backward words, shorter switchbacks tend to be less interesting. It's fairly easy to find three-letter switchbacks, such as "now" (becoming "wow" or "wen") and "tea" (becoming "art")—you're changing one-third of the letters as you do the reversal. But four-letter switchbacks ("work" or "word" becoming "prow") are a little harder to find, and five-letter ones (or longer) are even harder. Here are a few:

  • adobe <—> ebola
  • deter <—> rated
  • dwarf <—> fraud
  • lemon <—> novel
  • lions <—> snail
  • names <—> semen
  • paper <—> recap

Note that the switchback process can never re-produce the original word. Changing two letters and reversing could take a near-palindromic word like "never," change the first and last letters to make "reven," and reverse to obtain the original word. But if you compare a word with its reversal, they always differ either in no letters (if the word is a palindrome) or in at least two letters; changing exactly one letter can never turn a word into its reverse.

There's a word-ladder game that many logophiles enjoy (Lewis Carroll was a well-known practitioner), involving turning one word into another word by changing one letter at a time, with each intermediate step also being a word. For instance, you can bring home the bacon by changing WORK into MEAT one letter at a time: work, fork, folk, fold, mold, meld, melt, meat. (By the way, you can sometimes turn a word backward by changing one letter at a time—you can change WARD into DRAW, for instance, in eight steps...) You can make the same sorts of ladders with switchbacks: NAVES, for instance, to SEVEN, to NEVER, to RAVEN. I don't know of any switchback ladders longer than four steps, but I haven't looked very hard.

My favorite switchback is the first one I came up with, back in high school: I noticed that if you turn "flowered" backwards and change one letter, you get "werewolf." Who ever said Dungeons & Dragons® wasn't educational?

Addendum: I've written a Perl program that takes a word as input and (by brute force) checks all switchback possibilities to see if they're words, by looking them up in a given word file (like the /usr/dict/words file often found on UNIX systems). Note that this program is probably not the most efficient method of finding switchbacks, but it does seem to work. (Note particularly that if you run it on a system with other users, you probably ought to set it up to avoid hogging processor time, by using the nice utility or something.) Commentary and improvements are welcome. (One more note: I didn't use this program to find any of the above switchbacks.)

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