Three-letter acronym


A three-letter acronym, 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 ; three-letter abbreviations such as etc. and Mrs. are not three-letter acronyms, but "TLA" is a TLA.
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; computed axial tomography, 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

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
"Because 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 is 26 × 26 × 26 = 17,576. A additional 26 × 26 × 10 = 6760 can be produced if the third position is allowed to be a digit 0-9, giving a total of 24,336.
In standard English, WWW is the TLA whose pronunciation requires the most syllables -- typically nine. The usefulness of TLAs typically comes from it being quicker to say the acronym than the phrase it represents; however saying 'WWW' in English requires three times as many syllables as the phrase it is meant to abbreviate. Consequently, "www" is sometimes abbreviated as "dubdubdub" in speech.