An acronym is an abbreviation made up of the beginning letters of the words. It is usually also one which is pronounceable.

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Alternatively, an initialism is a term made up of the beginning letters of the words. It is usually also one which is pronounced by its letters.
A similar word is a backronym. A backronym is a blend of the word “back” and “acornym”.
Examples
Acronym
- Laser:Light Amplification by Stimulated Emission of Radiation
- Gestapo:Geheime Staatspolizei
- CD-ROM:Compact Disc Read-Only Memory
Initialism
- BBC: British Broadcasting Corporation
- USA: United States of America
- PIN: Personal Identification Number
Backronym
- SAD-Seasonal Affective Disorder
- COVFEFE Act- Communications Over Various Feeds Electronically For Engagement Act
- SOS-Save Our Ship/Soul