A hapax legomenon (pl. hapax legomena, though sometimes called hapaxes for short) is a word that occurs only once in the corpus of a language. (Occurrence in a dictionary that cites the occurrence in the corpus does not count.) Some of these are misspellings; others are real words that are rare enough that they only got used once. If a word is used twice it is a dis legomenon, thrice tris legomenon. Beyond tetrakis legomenon, a word isn't rare enough to call it that.
Some examples:
- "Nortelrye" is a word for "education" found only in Chaucer.
- "autoguos" (αυτογυος) is an ancient Greek word for a plow, found only in Hesiod, whose precise meaning is obscure
The term in its loose usage is popular among Bible scholars, who take the number of hapaxes in a putative author's corpus as an indication of his vocabulary and thereby argue for or against attribution. The identification of a word as a hapax by these authors means only that it occurs once in the Bible or yet more narrowly, once in the New Testament, rather than indicating that it occurs once in a language.