An acronym is an abbreviation pronounced as a single word. Words that are formed using the initial letters of a multi-word term are acronyms.
Thus, all acronyms are abbreviations, but strictly speaking, not all abbreviations are acronyms. An abbreviation could also be an initialism, in which the letters are individually pronounced (e.g., USA, ATM, CEO, DNA), a contraction (Dr., Jr., St.), or other shortened form (Inc., Corp., Jan.).
Overlap in meaning
In everyday usage, the word acronym has come to mean the same as abbreviation, and the two words are often used interchangeably. This overlap in meaning is reflected in modified dictionary definitions: Merriam-Webster now lists the meaning of acronym not only as a word made using the initial letters of a term but also as any abbreviation, including an initialism. In contrast, the OED, for now, retains the distinction between acronym and abbreviation.
We discuss below how acronyms are treated differently from other abbreviations in edited text, and why it is still useful for editors and writers to distinguish between the two.
Acronyms vs. other abbreviations at start of sentence
An abbreviation is not generally used to start a sentence in academic and other formal writing. We use the full form instead, or rephrase. Acronyms however are acceptable in this position.
- Poor: LRS readings were not available.
Avoid starting a sentence with an abbreviation that is an initialism (individual letters pronounced).Better: Readings from long-range sensors were not available.
Also acceptable: Long-range sensor readings were not available.
- Acceptable: NASA readings indicate that this was the hottest July on record.
Since NASA is pronounced as a word (i.e., it is an acronym), it is fine to use at the start of a sentence.
Use of the definite article the
It is also useful to distinguish between an acronym and an initialism when you intend to use the article the. The definite article the is not generally used before a proper noun that is an acronym (even if it would be used before the full form) but is used before an initialism.
- With initialism: Farley lives in the USA.
- With acronym: Farley works at
Note how if the full form were used instead of the acronym, the article the would still be used, but once the term becomes an acronym and is pronounced as a word, the definite article disappears, as it would before another proper-noun word.
- The National Aeronautics and Space Administration is responsible for the US civil space program.
TheNASA launched another satellite today.
- The North Atlantic Treaty Organization is an intergovernmental military alliance.
TheNATO is staying out of the conflict.
Differences in capitalization
Capitalization may also differ. In British usage, acronyms are often written as words, with proper nouns retaining only the initial capital letter. Not so with initialisms, where all the letters of the term must be capitalized.
One of the reasons Wednesday’s meeting is so noteworthy is Nasa’s change of approach. The space agency spent decades debunking UFO sightings.— “UFOs: Five revelations from Nasa’s public meeting,” BBC News (June 1, 2023)
A group of Nato countries may be willing to put troops on the ground in Ukraine if member states including the US do not provide tangible security guarantees to Kyiv.— “Nato members may send troops to Ukraine, warns former alliance chief,” Guardian (June 7, 2023)
Even in non-British usage, acronyms that are five letters or longer generally lose their capitalization, although those that are proper nouns retain the initial capital letter. For example, COVID may be written with capital or lowercase letters—COVID, Covid, or even covid—per Merriam-Webster. Initialisms, unlike acronyms, stay capitalized—for example, AIDS or Aids, but HIV, not Hiv.
Acronyms as words
Acronyms can even sometimes turn into words in their own right (none of the letters capitalized), with people forgetting they were ever abbreviations.
- laser: light amplification by stimulated emission of radiation
- radar: radio detection and ranging
- sonar: sound navigation and ranging
- scuba: self-contained underwater breathing apparatus
Go ahead and look up the origins of the words fubar and snafu in the dictionary.