Heterogram (literature)

A heterogram is a word, phrase, sentence, or longer text in which no letter of the alphabet is repeated. The term is most often applied to sentences or phrases, although it can technically apply to words as well. The challenge in creating heterograms, especially longer ones, lies in using common vocabulary and grammatically correct sentence structure while adhering to the constraint of non-repetition.

Heterograms are often considered a form of constrained writing, similar to palindromes or lipograms. Unlike pangrams, which seek to include every letter of the alphabet, heterograms strive for maximum uniqueness within a given text. The pursuit of long and meaningful heterograms is a word puzzle pastime enjoyed by logophiles. The length and coherence of a heterogram are often used as metrics of its impressiveness.

The term itself is derived from Greek roots, with "hetero" meaning "different" and "gram" meaning "letter."