A word with no repeated letters is called an isogram. The longest examples in our dictionary run to fifteen letters, including DERMATOGLYPHICS, the study of fingerprint patterns, and UNCOPYRIGHTABLE, meaning something that cannot legally be copyrighted.
The longest isograms we could find
Fifteen letters, no repeats:
Fourteen letters, no repeats:
Why long isograms are so rare
English has 26 letters total, so a word longer than 26 letters could never be a true isogram no matter what. In practice, it gets difficult long before that ceiling, since common letters like E, S, A and T show up repeatedly in almost every long English word by default. A word that avoids repeating any letter at all, while still being a genuine, recognizable word, is a genuine rarity once you get past ten or eleven letters.
What DERMATOGLYPHICS actually means
It refers to the study of the patterns found in fingerprints, palm prints, and footprints, both for identification purposes and in some medical research contexts. At fifteen letters with zero repeats, it's frequently cited as one of the longest common isograms in English.
Try finding your own
Our Check Dictionary tool confirms whether any word you're curious about is valid in our dictionary, which is a quick way to verify a potential isogram you've spotted on your own.
Frequently asked questions
What is an isogram?
A word in which no letter repeats. Every single letter in the word appears exactly once.
What's the longest isogram in English?
Candidates vary depending on which dictionary you check, but words around fifteen letters, like DERMATOGLYPHICS and UNCOPYRIGHTABLE, are commonly cited as some of the longest widely recognized examples.
Why are long isograms so hard to find?
Common English letters like E, A, S and T tend to repeat naturally in longer words, so avoiding any repetition at all becomes statistically less likely the longer a word gets.
Is there a theoretical maximum length for an isogram?
Since English has 26 letters, no isogram in a single-alphabet sense could exceed 26 letters, though in practice genuine examples run out of steam well before that.
Are isograms useful for anything besides trivia?
They show up in some cryptography and puzzle design contexts, and they're a popular category in word game trivia and vocabulary challenges.
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