three letter rule

(XX^e siècle) Composé de three, letter et rule.

three letter rule \ˌθɹi ˌlɛt.ɚ ˈɹul\ (États-Unis), \ˌθɹiː ˌlɛt.ə ˈɹuːl\ (États-Unis)

1. (Linguistique) Convention de typographie anglaise établie au xvii^e siècle consistant à écrire les mots lexicaux avec au moins trois lettres, avec un e muet (bye, die, etc.), par réduplication de la consonne finale (egg, inn, odd, etc.) ou avec un digramme (low, too, etc.) pour les différencier des mots-outils à deux lettres.
   • Lexical words usually have a minimum of three letters
     Both ‹e›-marking and ‹C›-doubling have another function in that they are used to bulk up the spelling of monosyllabic lexical words to a minimum of three letters (Jespersen 1909: 4.96). This is referred to as ‘the short word rule’ or ‘the three letter rule’. Albrow cites this as one of the factors differentiating the main subsystems of lexical words from the subsystem of function words, in which the rule does not apply. Jespersen himself interprets the convention as essentially a marking of phonetic ‘quantity’ in that be, by, in, an (compared with bee, bye, inn, Ann) usually occur as unstressed syllables and are physically reduced compared with the equivalent stressed forms. — (Edward Carney, A Survey of English Spelling, 2012, ISBN 9781134872237, page 133)
   • The three letter rule describes how only structure words can consist of a single letter—‘I’ and ‘a’—or two letters—‘an’ and ‘no’; content words have three letters or more. — (Vivian Cook, Second Language Learning and Language Teaching, 5^e édition, 2016, ISBN 9781134683222, page 116)

• three-letter rule

• short word rule

• three letter rule sur l’encyclopédie Wikipédia (en anglais)