Three-letter acronym

Three-letter acronym
A three-letter acronym (TLA), or three-letter abbreviation, is an abbreviation 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, but "TLA" is a TLA (an example of an autological abbreviation).
Most three-letter abbreviations are not, strictly, acronyms, but rather initialisms: all the letters are pronounced as the names of letters, as in APA . Some are true acronyms, pronounced as a word: as with computed axial tomography, for example, CAT is almost always pronounced as the animal's name in "CAT scan". Even the initialisms are however considered three-letter acronyms, because that term appeared first in widespread use, and is overwhelmingly popular today.
Examples
Academic testing: ACT, SAT
Air Navigation Services (ANS): AIS, ASM, ATC, ATM, ATS, CNS, FIS, FPC, MET, and SAR
IATA airport codes: LAX and LHR
Business: CEO, CFO, and other C-level officers
Canine registries: AKC and CKC
Chemistry, biology, and pharmaceuticals: GMO, LSD, and MSG
Clinical medicine: CAD, CHF, PSA, and SOB
Communications shorthand: LOL and OMG
Computer phrases: CPU, DOS, RAM, ROM, and GNU
Corporations: BMW, IBM, AMD, and NEC
Countries: SRI, USA, CAR, UAE, DRC, etc.
Currency: USD, GBP, and CHF
Famous people: FDR, JFK, MJK, MLK, OBL, RBG, RDJ, and RMS
File extensions: JPG, PDF, and XLS
Military and weaponry: BFR and RPG
Musical groups: R.E.M., XTC, TLC, E.L.O., MC5, GBH, O.A.R., MDC, D.R.I., JFA
Personal advertisements: SBM for Single Black Male, STR for Short Term Relationship
Political Parties: BJP, CCP, GOP, and AAP
Religion: LDS, SBC, and SDA
Ship prefixes: HMS, USS, and RMS
Sports organizations: NFL, MLB, (North America); AFL, and NRL (Australia); NPB (Japan); ACB, LFP (Spain); IPL (India), EPL (England), WBO
State postal abbreviations: NSW, QLD, VIC, and TAS (Australia)
Television networks: ABC (Australia, U.S.), BBC (UK), CBC (Canada, Japan), and NHK (Japan)
Three Letter Agencies: CIA, FBI, CBI, FSB, and NSA
Wars and political conflicts: HYW and WWI
History and origins
The exact phrase three-letter acronym appeared in the sociology literature in 1975. Three-letter acronyms were used as mnemonics in biological sciences, from 1977 and their practical advantage was promoted by Weber in 1982. They are used in many other fields, but the term TLA is particularly associated with computing. In 1980, the manual for the Sinclair ZX81 home computer used and explained TLA. The specific generation of three-letter acronyms in computing was mentioned in a JPL report of 1982. 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" By 1992 it was in a Microsoft handbook.
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. An additional 26 × 26 × 10 = 6760 can be produced for each single position allowed to be a digit 0-9, such as 2FA, P2P, or WW2, giving a total of 37,856 such three-character strings.
In standard English, WWW is the TLA whose pronunciation requires the most syllables—typically nine. The usefulness of TLAs 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.
See also
Acronym
Alphabet agencies
ISO 4217 (currency code)
List of abbreviations in photography
List of computing and IT abbreviations
List of three-letter broadcast call signs in the United States
List of three-letter combinations having Wikipedia articles
Lists of acronyms
Lists of airports by IATA and ICAO code
Q code
Recursive acronym
RAS syndrome
References
Abbreviations
T