# Hapax legomenon · writing glossary · ScriptGrain > A hapax legomenon is a word that occurs exactly once within a given context: a single text, an author's complete works, or a language's entire written record. From Greek, 'said once'; plural: hapax legomena. Canonical: https://scriptgrain.com/glossary/hapax-legomenon # Hapax legomenon A hapax legomenon is a word that occurs exactly once within a given context: a single text, an author's complete works, or a language's entire written record. From Greek, 'said once'; plural: hapax legomena. ## The numbers - Share of distinct words in large corpora that are hapax legomena (per Zipf's law): **about 40% to 60%** ([Wikipedia: Hapax legomenon](https://en.wikipedia.org/wiki/Hapax_legomenon)) - Share of distinct words that are dis legomena (occur twice) in large corpora: **about 10% to 15%** ([Wikipedia: Hapax legomenon](https://en.wikipedia.org/wiki/Hapax_legomenon)) - Hapax legomena in the Brown Corpus of American English: **roughly half of its 50,000 distinct words** ([Wikipedia: Hapax legomenon](https://en.wikipedia.org/wiki/Hapax_legomenon)) - Distinct words in Moby-Dick that occur only once: **about 44%** ([Wikipedia: Hapax legomenon](https://en.wikipedia.org/wiki/Hapax_legomenon)) ## Definition A hapax legomenon (Greek for 'said once'; plural hapax legomena, often just 'hapaxes') is a word or expression that occurs exactly once within a defined context. The context matters: a word can be a hapax within one text, within an author's complete works, or within the entire written record of a language, and the claim means something different in each case. The family extends upwards: a dis legomenon occurs twice, a tris legomenon three times, and a tetrakis legomenon four times. ## Hapaxes are the norm, not the exception Intuition says a word used only once must be unusual. Corpus statistics say the opposite. In line with Zipf's law, roughly 40% to 60% of the distinct words in a large corpus are hapax legomena, and a further 10% to 15% are dis legomena. In the Brown Corpus of American English, about half of the roughly 50,000 distinct words occur exactly once, and in Moby-Dick about 44% of the distinct words appear only once. What carries information is therefore not the existence of hapaxes but their rate: the proportion of a text's vocabulary used only once, compared against samples of similar length. A high hapax rate signals a writer reaching for fresh words rather than recycling a small working vocabulary. ## Use in authorship analysis, and its limits Hapax counting has a long history in authorship studies; P. N. Harrison popularised its use on Biblical texts. As a standalone attribution method it has faded, because hapax frequency is affected by text length, topic, audience and date of composition, so a difference between two texts can have mundane explanations. Modern stylometry treats the hapax rate as one lexical-richness signal among many rather than a fingerprint on its own. In computational language processing, hapaxes are often simply discarded from models, since a single occurrence provides little statistical value. ## Worked example Take this 15-word passage: 'I know what I know, and what I know is that nothing here changes quickly.' The passage has 15 tokens and 10 types. Frequencies: 'I' three times, 'know' three times, 'what' twice, and seven words exactly once each: and, is, that, nothing, here, changes, quickly. Those seven are the hapax legomena, and 'what' is a dis legomenon. Hapax rate: 7 / 10 = 70% of types, or 7 / 15 = 47% of tokens. Even a deliberately repetitive sentence is mostly hapaxes when counted by type. Always state the basis, per type or per token, when quoting a hapax rate; the two figures differ widely. ## Sources - [Wikipedia: Hapax legomenon](https://en.wikipedia.org/wiki/Hapax_legomenon) ## More terms - [Voice Match](https://scriptgrain.com/glossary/voice-match) - [Burstiness](https://scriptgrain.com/glossary/burstiness) - [Perplexity](https://scriptgrain.com/glossary/perplexity) - [Sentence Length Variance](https://scriptgrain.com/glossary/sentence-length-variance) - [Flesch Reading Ease](https://scriptgrain.com/glossary/flesch-reading-ease) - [Type-token ratio (TTR)](https://scriptgrain.com/glossary/type-token-ratio) - [Function words](https://scriptgrain.com/glossary/function-words) - [Lexical density vs lexical diversity](https://scriptgrain.com/glossary/lexical-density-diversity) - [Stylometric fingerprint](https://scriptgrain.com/glossary/stylometric-fingerprint) - [Idiolect](https://scriptgrain.com/glossary/idiolect) - [Voice vs tone vs style](https://scriptgrain.com/glossary/voice-tone-style) - [Passive voice](https://scriptgrain.com/glossary/passive-voice) - [Humanised AI content](https://scriptgrain.com/glossary/humanised-ai-content) - [Tone matching](https://scriptgrain.com/glossary/tone-matching) - [Brand voice](https://scriptgrain.com/glossary/brand-voice) - [Voice drift](https://scriptgrain.com/glossary/voice-drift)