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A palindrome is a word, phrase, verse or sentence that reads the same backward or forward. In 2002, Peter Norvig read that Dan Hoey had created a computer program that had generated a 540 word palindrome in 1984. Thinking he could do one better, Norvig created his own version of the program. Both programs were based off of the classic phrase “A man, a plan, a canal: Panama.” The algorithm puts words into the middle of the sentence while keeping the same beginning and end to make sure it is a palindrome. On Norvig’s first try he was able to make a 15,139 word palindrome; after a bit of tweaking he created he created a 17,259 word palindrome, the longest one to date.

Single-word palindromes are equally interesting. Finnish has the longest single-word palindromes, with two entries: “saippuakivikauppias,” which means “soap stone dealer”; and “solutomaattimittaamotulos,” which means “the result from a measurement laboratory for tomatoes.” Depending on who you ask, “tattarrattat,” “kinnikinnik,” or “detartrated” is the longest single-word palindrome in English, though some would say these words are not really part of the English language, since they are contrived or almost never used.

For more information:
Peter Norvig’s 17,259 Word Palindrome
Wikipedia Entry on Palindromes
The Palindromist Magazine