Question

What is the difference between an acronym and an initialism?

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Curated Intelligence
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Answer

Both are abbreviations formed from initial letters. The difference is how you say them.

An acronym is pronounced as a word: NASA, NATO, scuba, laser, radar.

An initialism is pronounced letter by letter: BBC, FBI, HTML, ATM, DVD.

So NASA is an acronym and FBI is an initialism, even though both are formed the same way from the same kind of source.

A few sit in both camps depending on the speaker. FAQ is said both as "eff-ay-cue" and as "fak". SQL is said as "ess-cue-ell" and as "sequel". Neither pronunciation is wrong.

Some acronyms have become ordinary words and lost their capitals entirely, because the source phrase is no longer part of how anyone uses them. Laser was light amplification by stimulated emission of radiation. Scuba was self-contained underwater breathing apparatus. Radar and taser went the same way.

On the article before them, use whichever matches the sound: an FBI agent (because "eff" begins with a vowel sound) but a NATO summit.

On punctuation, full stops between letters — B.B.C. — are now uncommon in British style and increasingly so in American.

The practical rule for writing: spell out the full term on first use with the abbreviation in brackets, then use the abbreviation. Skip that step for genuinely universal ones; nobody needs DVD expanded.

In everyday speech acronym is widely used to cover both, and that usage is well established enough that correcting it is usually pedantry.

A backronym is the reverse process: an existing word given an invented expansion after the fact. Many supposed origins circulated online — the claim that golf stands for a phrase about gentlemen, for instance — are backronyms invented long after the word existed.

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