A heterogram (from hetero-, meaning "different", + -gram, meaning "written") is a word, phrase, or sentence in which no letter of the alphabet occurs more than once.
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An isogram, in which all letters occur an equal number of times, is the same as a heterogram when each letter occurs once.
A heterogram may be distinguished from a pangram (a holoalphabetic sentence), which uses all of the letters of the alphabet (possibly more than once). A perfect heterogram is, however, the same as a perfect pangram, since both consist of all letters of the alphabet with each represented exactly once.
Abjads and abugidas, in which only the consonants are represented in the basic graphemes, have a naturally high incidence of heterograms.
One word
9 letters
capsuling, carpeting, certainly, clavering, constable, coxalgies, cravingly, expulsing, flowchart, franticly, interplay, lacewings, lawyering, neuralgic, overmatch, packeting, paltering, panegyric, parceling, parleying, pecuniary, picayunes, preacting, prelaunch, privately, puckering, racketing, repacking, replacing, replating, replaying, sluiceway, Spaulding, squawking, squeaking, squealing, traveling, unshapely, vectorial.
10 letters
caperingly, lacqueying, taperingly, dumbwaiter
15 letters
uncopyrightable
17 letters
subdermatoglyphic