A three-letter acronym (TLA), or three-letter abbreviation, is as the phrase suggests an abbreviation consisting of three letters. The abbreviation for TLA, TLA, has a special status among abbreviations and to some is humorous since abbreviations that are three-letters long are very common and TLA is, in fact, a TLA.
Most TLAs are initialisms (the initial letter of each word of a phrase), but most are not acronyms in the strict sense since they are pronounced by saying each letter, as in APA/ˌeɪpiːˈeɪ/AY-pee-AY. Some are true acronyms (pronounced as a word) such as CAT (as in CAT scan) which is pronounced as the animal.
The exact phrase three-letter acronym appeared in the sociology literature in 1975.[1] Three-letter acronyms were used as mnemonics in biological sciences, from 1977[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] In 1980, the manual for the Sinclair ZX81 home computer used and explained TLA.[5] The specific generation of three-letter acronyms in computing was mentioned in a JPL report of 1982.[6] In 1988, in a paper titled "On the Cruelty of Really Teaching Computing Science", eminent computer scientist Edsger W. Dijkstra wrote (disparagingly), "No endeavour is respectable these days without a TLA"[7] By 1992 it was in a Microsoft handbook.[8]
Combinatorics
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. Allowing a single digit 0-9 increases this by 26 × 26 × 10 = 6,760 for each position, such as 2FA, P2P, or WW2, giving a total of 37,856 such three-character strings.
Out of the 17,576 possible TLAs that can be created using 3 uppercase letters, at least 94% of them had been used at least once in a dataset of 18 million scientific article abstracts. Three-letter acronyms are the most common type of acronym in scientific research papers, with acronyms of length 3 being twice as common as those of length 2 or 4.[9]
In standard English, WWW is the TLA whose pronunciation requires the most syllables—typically nine. The usefulness of a TLA typically comes from its being quicker to say than the phrase it represents; however saying 'WWW' in English requires three times as many syllables as the phrase it is meant to abbreviate (World Wide Web). "WWW" is sometimes abbreviated to "dubdubdub" in speech.[10]
^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. Bibcode:1977JBiog...4...55S. doi:10.2307/3038128. JSTOR3038128. All taxa indicated by three-letter acronyms with strains indicated by a fourth letter if necessary.
^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. doi:10.2307/1220592. JSTOR1220592.
^Nilsen, K. D.; Nilsen, A. P. (1995). "Literary Metaphors and Other Linguistic Innovations in Computer Language". The English Journal. 84 (6): 65–71. doi:10.2307/820897. JSTOR820897.
^Steven VickersZX81 Basic Programming, Sinclair Research Limited, page 161 "As you can see, everything has a three letter abbreviation (TLA)."
^TDA Progress Report R. Hull (1982) An Introduction to the new Productivity Information Management System page 176
