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Q: What exceptional words turn into other words by substitution of letters?

A: longest onalosi (substitution in every position possible)
 BANDIES:CANDIES->BUNDIES->BADDIES->BANGIES->BANDSES->BANDITS->BANDIED (7)
 BROWSES:CROWSES->BLOWSES->BREWSES->BROOSES->BROWZES->BROWSTS->BROWSED (7)
 CARACAS:MARACAS->CURACAS->CAMACAS->CARICAS->CARANAS->CARACKS->CARACAL (7)
 CLASSES:GLASSES->CHASSES->CLESSES->CLADSES->CLASHES->CLASSIS->CLASSED (7)
 COLLIES:BOLLIES->CALLIES->COALIES->COLBIES->COLLSES->COLLINS->COLLIED (7)
 PASTERS:BASTERS->PESTERS->PALTERS->PASSERS->PASTORS->PASTELS->PASTERN (7)
shortest isolano (no substitution possible)
 EPI (3)
longest word, all letters changed to other letters in minimum number of
steps, yielding another word  THUMBING-THUMPING-TRUMPING-TRAMPING-
 TRAPPING-CRAPPING-CRAPPINS-CRAPPIES-CRAPPOES  (8)
longest word girders  BADGER/SUNLIT, BUDLET/SANGIR (6)
longest word with full vowel substitution
 BATTINGS->BETTINGS->BITTINGS->BOTTINGS->BUTTINGS (8)
 CLACKING->CLECKING->CLICKING->CLOCKING->CLUCKING (8)
 RACKLING->RECKLING->RICKLING->ROCKLING->RUCKLING (8)
 and Y
  CATES->CETES->CITES->COTES->CUTES->CYTES (5)
  DANES->DENES->DINES->DONES->DUNES->DYNES (5)
  MARAS->MARES->MARIS->MAROS->MARUS->MARYS (5)
longest words with vowel substitutions
 DESTRUCTIBILITIES, DISTRACTIBILITIES (17)
longest word constant-letter-shifted to another PRIMERO-SULPHUR (7)
 arithmetical-letter-shifted DREAM-ETHER (5)
 constant-shift-with-transposal (shiftgrams) AEROPHANE-SILVERITE (9)
longest word pair shifted one position on typewriter keyboard WAXIER-ESCORT (6)
longest word pair confusable on a telephone keypad AMOUNTS-CONTOUR (7)
''''''''''''
Unless noted otherwise, all words occur in Webster's Third New International
Dictionary, Merriam-Webster, Springfield, MA, 1961.
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