What is the longest word in the english dictionary that does not use the same letter twice?
The kind of word you ask about, one in which no letter of the alphabet appears more than once, is called a ‘nonpattern’ word and belongs to a larger group of words called ‘isograms.’ Isograms are words with a particular letter pattern, or, as in the case of ‘ambidextrously,’ the lack of a pattern. ‘Ambidextrously,’ which contains 14 letters, is certainly one of the longest nonpattern words. Another 14-letter nonpattern word is ‘hydropneumatic,’ defined in Webster’s Third New International Dictionary as ‘of, relating to, or operating by means of both water and air or some other gas.’ We are aware of only one word entered in the Third New International that surpasses the fourteen-letter mark: ‘dermatoglyphics,’ a fifteen-letter noun that means ‘patterns of the specialized skin of the inferior surfaces of the hands and feet’ or ‘the study of such patterns.
