Three-letter acronym

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A three-letter acronym, three-letter abbreviation, or TLA is an abbreviation, specifically an acronym, alphabetism, or initialism, consisting of three letters. These are usually the initial letters of the words of the phrase abbreviated, and are written in capital letters (upper case); three-letter abbreviations such as etc. and Mrs. are not three-letter acronyms.

Most three-letter abbreviations are initialisms: all the letters are pronounced as the names of letters, as in APA /ˌpˈ/ AY-pee-AY. Some are acronyms pronounced as a word; computed axial tomography, CAT, is almost always pronounced as the animal's name in "CAT scan".


Further information: Category:Lists of TLAs

History and origins[edit]

The exact phrase three-letter acronym appeared in the literature in 1975.[1] Three-letter acronyms were used as mnemonics in biological sciences,[2] and their practical advantage was promoted by Weber in 1982.[3] They are used in many other fields, but the term TLA is particularly associated with computing.[4] The specific generation of three-letter acronyms in computing was mentioned in a JPL report of 1982.[5]

In 1980, the manual for the Sinclair ZX81 home computer used and explained TLA.[6] In 1988, in a paper titled "On the cruelty of really teaching computer science", eminent computer scientist Edsger W. Dijkstra wrote "Because no endeavour is respectable these days without a TLA ..."[7] By 1992 it was in a Microsoft handbook.[8]

Use of "TLA" spread through both industry and academia, and it has now become a generally understood initialism.


The number of possible three-letter abbreviations using the 26 letters of the alphabet from A to Z (AAA, AAB ... to ZZY, ZZZ) is 26 × 26 × 26 = 17,576. Another 26 × 26 × 10 = 6760 can be produced if the third element is allowed to be a digit 0-9, giving a total of 24,336.

In English, WWW is the longest possible TLA to pronounce, typically requiring nine syllables. Although in written English it is an abbreviation, in spoken English it ordinarily uses three times as many syllables than the words it is abbreviating, World Wide Web, which is three syllables.[citation needed]

References in popular culture[edit]

See also[edit]


  1. ^ Levy, M. J. (1975). "Review of The Logic of Social Systems". American Journal of Sociology 81 (3): 658. JSTOR 2777655. The acronyms DSE and DNA have something in common: each is a three-letter acronym. 
  2. ^ Seavey, S. R.; Raven, P. H. (1977). "Chromosomal Differentiation and the Sources of the South American Species of Epilobium (Onagraceae)". Journal of Biogeography 4 (1): 57. JSTOR 3038128. All taxa indicated by three-letter acronyms with strains indicated by a fourth letter if necessary. 
  3. ^ Weber, W. A. (1982). "Mnemonic Three-Letter Acronyms for the Families of Vascular Plants: A Device for More Effective Herbarium Curation". Taxon 31 (1): 74–88. JSTOR 1220592. 
  4. ^ Nilsen, K. D.; Nilsen, A. P. (1995). "Literary Metaphors and Other Linguistic Innovations in Computer Language". The English Journal 84 (6): 65–71. JSTOR 820897. 
  5. ^ TDA Progress Report R. Hull (1982) An Introduction to the new Productivity Information Management System page 176
  6. ^ Steven Vickers ZX81 Basic Programming, Sinclair Research Limited, page 161 "As you can see, everything has a three letter abbreviation (TLA)."
  7. ^ On the cruelty of really teaching computer science
  8. ^ Dan Gookin (1992) The Microsoft Guide to Optimizing Windows page 211
  9. ^ Lyrics of "MfG"
  10. ^ Douglas Adams, The Independent on Sunday, 1999
  11. ^ TLA the band