Definition · Plain-language
Acronym
An acronym is a word formed from the initial letters of a phrase and pronounced as a single word, such as NASA, radar or scuba.
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Initials pronounced as a word
An acronym is built from the initial letters (and sometimes initial sounds) of a multi-word name or phrase, then pronounced as if it were an ordinary word. NASA stands for the National Aeronautics and Space Administration, and we say it "NASA", not "N-A-S-A". Some acronyms have become so familiar that their origin is forgotten and they are written in lower case: laser (light amplification by stimulated emission of radiation), radar (radio detection and ranging) and scuba (self-contained underwater breathing apparatus) are everyday words whose acronymic roots many speakers never think about. Acronyms compress long official names into something memorable and easy to say.
Acronym versus initialism
The key distinction is pronunciation. An acronym is read as a single word (NATO, UNESCO); an initialism is spelled out letter by letter (FBI, BBC, HTML, DIY). Both are abbreviations formed from initial letters, which is why the two are often confused, and in loose usage "acronym" is sometimes applied to both. Careful writers reserve acronym for the pronounced-as-a-word kind. A few abbreviations are hybrids — JPEG is part-sounded, part-spelled — and some, like SQL, are pronounced both ways by different communities. The grammar of articles follows the sound, not the spelling: "an NHS hospital" (sounded "en") but "a NASA mission".
Forming and writing acronyms
Most acronyms take the first letter of each significant word, though some include extra letters to make a pronounceable result — radar and scuba keep internal letters for this reason. Convention on capitalisation varies: organisational acronyms are usually all capitals (NATO), while fully absorbed ones become lower case (laser). A backronym is a playful reverse-engineering, where a word is treated as if its letters stood for something they did not originally — inventing an expansion to fit an existing word. Acronyms are a sub-type of abbreviation, alongside initialisms, clippings (such as app) and contractions; what defines the acronym specifically is being read aloud as a word.
Key facts
At a glance
- Definition: initials of a phrase pronounced as a single word
- Examples: NASA, laser, radar, scuba, NATO
- Contrast: an initialism is spelled out — FBI, BBC, DIY
- Both are: types of abbreviation from initial letters
- Spelling: fully absorbed acronyms become lower case (laser)
- Backronym: an expansion invented to fit an existing word
Common misconceptions
What people often get wrong
Often heard: Any abbreviation made from initial letters is an acronym.
Actually: Strictly, an acronym is pronounced as a word (NASA, radar). An abbreviation whose letters are sounded individually — FBI, BBC, HTML — is an initialism. The difference is whether you read it as a word or spell it out.
Often heard: Acronyms must always be written in capital letters.
Actually: Many fully absorbed acronyms are lower case: laser, radar and scuba are ordinary words. Capitalisation depends on how established the acronym has become, not on it being an acronym.
Often heard: The expansion of an acronym is always its true historical origin.
Actually: A backronym is an expansion invented after the fact to fit an existing word. Not every neat expansion reflects how the term was actually coined.
Going deeper
