Abbreviations, acronyms, and initialisms

FAQs, ATMs and RSVPs – what are these words in English? Abbreviations, acronyms and initialisms can get confusing for everyone, and social media and instant messaging has opened up a whole new world of communicating that can be daunting even for English speakers.

Abbreviations, Acronyms, And Initialisms

We have a lot of acronyms, abbreviations and initialisms in English, which we assume most people understand. But even for native speakers, it’s not clear what the difference between these three are, and many of them actually come from other languages!

Abbreviations are shortened forms of words or phrases. Acronyms and initialisms are both types of abbreviations, but there is a difference between them.

According to, an acronym is “an abbreviation of several words in such a way that the abbreviation itself forms a pronounceable word. The word may already exist or it can be a new word.” There are some famous and international words that few people know were actually formed by putting words or letters together and shortening them, such as;   

  • Radar = radio detection and ranging
  • Laser = light amplification by the stimulated emission of radiation
  • Scuba = self-contained underwater breathing apparatus
  • Initialisms, on the other hand, are made up (usually) of the first letters of a group of words, but the key difference between an initialism and an acronym is that they do not form a whole new word (as above with radar, laser and scuba).
  • Here are some common ones you will almost certainly encounter, if you have not already:
  • FAQs = Frequently Asked Questions

Abbreviations, Acronyms, And Initialisms

Today's topic is the difference between abbreviations, acronyms, and initialisms. It's kind of an extension of the last episode, because I want to clarify the difference between abbreviations and acronyms.

Abbreviations and Acronyms

Any shortened form of a word is an abbreviation, for example, etc. for etcetera and Oct. for October; but acronyms are special kinds of abbreviations, such as ROFL (rolling on the floor laughing) and OPEC (Organization of Petroleum Exporting Countries), that can be pronounced as words. This makes them a subset of abbreviations. All acronyms are abbreviations, but not all abbreviations are acronyms.


Initialisms are another type of abbreviation. They are often confused with acronyms because they are made up of letters, so they look similar, but they can't be pronounced as words.

FBI and CIA are examples of initialisms because they're made up of the first letters of Federal Bureau of Investigation and Central Intelligence Agency, respectively, but they can't be pronounced as words.

NASA, on the other hand, is an acronym because even though it is also made up of the first letters of the department name (National Aeronautics and Space Administration), it is pronounced as a word, NASA, and not by spelling out the letters N, A, S, A.

So remember:

  • Initialisms are made from the first letter (or letters) of a string of words, but can't be pronounced as words themselves. Examples include FBI, CIA, FYI (for your information), and PR (public relations).
  • Acronyms are made from the first letter (or letters) of a string of words but are pronounced as if they were words themselves. Examples include NASA, NIMBY (not in my backyard), and hazmat* (hazardous materials).
  • Abbreviations are any shortened form of a word.

Style Guide

Finally, there's no strict rule about putting periods after each letter in an acronym or initialism.

Some publications put periods after each letter, arguing that because each letter is essentially an abbreviation for a word, periods are necessary.

Other publications don't put periods after each letter, arguing that the copy looks cleaner without them, and that because they are made up of all capital letters, the fact that they are abbreviations is implied.

That's all. As always, this is Grammar Girl, striving to be your friendly guide in the writing world.


Wikipedia Entry for Acronyms and Initalisms entry for Initialism An excellent discussion by HTML developers about acronyms and abbreviations. List of Common Abbreviations Everyday Acronyms

* I haven't been able to find a definitive answer on the right way to write hazmat, but the U.S. government's Office of Hazardous Materials Safety writes it as hazmat so I'm sticking with that for now.

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Word or name made from the initial components of the words of a sequence
For the HTML tag, see HTML element § acronym.
For the use of acronyms on Wikipedia, see Wikipedia:Acronyms.

An acronym is a word or name formed from the initial components of a longer name or phrase, usually using individual initial letters, as in NATO (North Atlantic Treaty Organization) or EU (European Union), but sometimes using syllables, as in Benelux (Belgium, Netherlands and Luxembourg), or a mixture of the two, as in radar (RAdio Detection And Ranging).

Similarly, acronyms are sometimes pronounced as words, as in NASA or UNESCO, sometimes as the individual letters, as in FBI or ATM, or a mixture of the two, as in JPEG or IUPAC.

The broader sense of acronym inclusive of terms pronounced as the individual letters (such as “TNT”) is sometimes criticized, but it is the term's original meaning[1] and is in common use.

[2] Language authorities such as dictionary and style guide editors are not in universal agreement on the naming for such abbreviations—in particular it is a matter of some dispute whether the term acronym can be legitimately applied to abbreviations which are not pronounced “as words”—or the correct use of space, case, and punctuation. See the Nomenclature, Lexicography and style guides and Orthographic styling sections below.


The word acronym is formed from the Greek roots acr-, meaning “height, summit, or tip” and -onym, meaning “name”.

[3] This neoclassical compound appears to have originated in German, with attestations for the German form Akronym from as early as 1921.

[4] English language citations for acronym date to a 1940 translation of a Lion Feuchtwanger novel.[5]


Whereas an abbreviation may be any type of shortened form, such as words with the middle omitted (for example, Rd for road or Dr for Doctor), an acronym is formed from the first letter or first few letters of each word in a phrase (such as sonar, created from sound navigation and ranging). In addition to acronym, the terms initialism and alphabetism are also used for abbreviations formed from a string of initials.

Abbreviations, acronyms, and initialisms

In English, there are four main classifications of shortened words and phrases.


All types of shortened words and phrases are technically abbreviations, but we generally use this term to denote shortened words—for example, Dr. in place of Doctor, pars. in place of paragraphs, Found. in place of Foundation, lbs. in place of pounds, AK in place of Alaska.


Acronyms are formed from the initial letters of phrases or compound terms. For example, the word radar comes from radio detecting and ranging.

Some acronyms, such as radar and scuba (self-contained underwater breathing apparatus) become words in their own right and hence are uncapitalized and unpunctuated. Other acronyms, such as NATO, AIDS, and NAFTA, are capitalized because the original words are capitalized (e.g.

, North Atlantic Treaty Organization). In 21st-century English, they are usually unpunctuated (though some publications resist this trend).


Although acronyms are technically initialisms, we usually use this term to describe initial-letter abbreviations that are pronounced as letters rather than words—for example, CEO, a.k.a., FBI, r.p.m., and USA.

The trend with initialisms is away from using periods, although many publications use periods when the original words are uncapitalized (e.g., r.p.m. from rotations per minute, and e.g.

from the Latin loan phrase exempli gratia).


Contractions are formed by omitting one or more letters from a word or phrase and replacing the omitted letters with an apostrophe—for example, can’t for cannot, they’re for they are.

When to use abbreviations, acronyms and initialisms | Cochrane Community

In this manual, the term 'abbreviation' is used to cover abbreviations, acronym and initialisms. 

Use abbreviations sparingly. Only use abbreviations if they are widely known across the broad readership of Cochrane Reviews, are used frequently in a section or throughout the review, or enhance readability. Consider using an abbreviation only if the term has three or more words.

All abbreviations used in the '
Abstract', 'Plain language summary', 'Main text', and 'Authors' conclusions' should be redefined at the beginning of these sections. In figures and tables, all abbreviations should be listed at the end with their definitions.

If the review or document is long, it may be sensible to explain each abbreviation in each section of the text.

To use an abbreviation, write the full name in the first instance and follow it immediately by the abbreviated version in brackets. When something is better known by its abbreviation, it may be helpful to include the abbreviation even if the name occurs only once (e.g. World Health Organization (WHO)).

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Abbreviations should follow formatting conventions. Some terms, particularly statistical terms, are commonly abbreviated in Cochrane documents (see Common abbreviations), while others should be avoided (see Abbreviations to avoid). See also Frequently used names for names commonly used and abbreviated in Cochrane documents.

Only the common abbreviations that do not need to be defined may be used in review titles and headings without the full name needing to be written first.

When a term used in a title may be more commonly known under its abbreviated form, its abbreviation may be added in parentheses after the fully written term (e.g. 'A study of the World Health Organization (WHO) recommendations for hygiene').

Abbreviations are acceptable in headings if they have been defined previously, though it may be preferable to rearrange the wording of headings to avoid starting with abbreviations.

At the beginning of a sentence

While it is acceptable to use abbreviations at the beginning of a sentence, authors may find it preferable to rephrase sentences to avoid starting with abbreviations.

In tables and figures

It is convenient to abbreviate some words, such as number (no.) and versus (vs), in tables and figures, but it is preferable to write them in full in the review text.

Dealing with abbreviations, acronyms, and initialisms

Based on a writing tip I recently sent to my work colleagues.

NOTE: These are the rules based on our style guide and its referenced authorities. Your style guide may differ.


In accordance with [our style guide]:

  • Always write out in full any abbreviation/acronym/initialism (see Notes for the differences) the first time you use it in the main body of the document, then put the abbreviation in parentheses; e.g. Materials Offloading Facility (MOF). Exception: Do not write out in full common abbreviated measurement units (e.g. km).
  • After that first instance, you can use the abbreviation etc. (e.g. MOF) throughout the rest of the document, except in the References list (see Other Guidance below).


  • Don’t use punctuation between the letters of an acronym or initialism (e.g. CSIRO, not C.S.I.R.O.).
  • If the term is only used once or twice in the document, you probably don’t need to abbreviate it, unless you know your readers are more familiar with the abbreviation (e.g. GPS, PPE), in which case write it in full the first time with its abbreviation even if it’s only used once in the document.
  • If a term is used more than about five times in the document AND there’s an abbreviation for it, consider replacing the term with the abbreviation. But first consider your audience (e.g. some regulatory documents may want certain terms written in full every time).
  • If the term and abbreviation are first used inside parentheses (such as in a citation), then use square brackets for the abbreviation within the parentheses; e.g. ‘blah blah (Department of Environment and Conservation [DEC] 2007) blah blah’.
  • In the References list, write out the abbreviation etc. in full where it’s the authoring body or the publisher (e.g. ‘Department of Sustainability, Environment, Water, Population and Communities. 2012.’ not ‘SEWPaC. 2012.’)
  • Make sure all abbreviations etc. you use in the document are listed and defined in the Terms list. You still have to write each term in full the first time it’s used in the main body of the document.
  • If the term is capitalised (capped) because it’s the proper name of something (e.g. Materials Offloading Facility), then keep those capitals in the full version, but if the term is normally not capped (e.g. personal protective equipment), then only use caps in the abbreviation (e.g. PPE).
  • Follow the guidance for SI units for the abbreviation and capitalisation of units of measure; e.g. km/h not km/hr (see [especially the tables in Sections 2.1.2, 2.2.1, 2.2.2, and 4.1 of that document]).
See also:  Amount versus number

NOTES (from

  • Initialisms are made from the first letter (or letters) of a string of words, but can’t be pronounced as words themselves. Examples include FBI, CIA, FYI (for your information), and PR (public relations).
  • Acronyms are made from the first letter (or letters) of a string of words but are pronounced as if they were words themselves. Examples include NASA, NIMBY (not in my backyard), and hazmat (hazardous materials).
  • Abbreviations are any shortened form of a word.


abbreviation OR acronym? | Vocabulary

Dr – Co. – Ltd – c.o.d – NASA – laser – let's – DVD – radar – a.s.a.p. – etc. – FAQ – HTML – scuba – BBC – DVD – abbrv. – Aids – FBA – NSA – phone – DTRT – telly – Prof. – UK – approx. – don't – PTO

People often ask: “What's the difference between an abbreviation and an acronym?”

To answer this question, we need to understand that an acronym is just one type of abbreviation.

An abbreviation is a short form of a word or phrase. All of the short forms that you see above ↑ are abbreviations.

The four main types of abbreviation are:

  • shortenings
  • contractions
  • initialisms
  • acronyms


A shortening is an abbreviation where the end of the word has been cut off, for example:

full form
app application
ad advertisement
approx. approximately
Co. Company
Prof. Professor


A contraction is an abbreviation where the middle of the word or words has been cut out, for example:

full form
Blvd Boulevard
Dr Doctor
Ltd Limited
ft foot, feet
don't do not


An initialism is an abbreviation made from the initial (first) letters of a group of words. We say the initialism as separate letters, for example:

full form
BA Bachelor of Arts
BBC British Broadcasting Corporation
UN United Nations
DVD digital versatile disc
VIP very important person

Listen to how the initialisms are pronounced, letter by letter:


An acronym is an abbreviation made from the initial (first) letters of a group of words. We say the acronym as a word, not as separate letters, for example:

full form
Aids acquired immune deficiency syndrome
NASA National Aeronautics and Space Administration
UNESCO United Nations Educational, Scientific, and Cultural Organization
radar radio detection and ranging
scuba self-contained underwater breathing apparatus

Listen to how the acronyms are pronounced, as actual words:

Abbreviation, Acronym and Initialism


The label abbreviation refers to the practice of writing a word or phrase that could also be written out in full using only the letters of the alphabet. Examples are: Mr for mister, Dr for doctor and Capt for captain.

In British English full stops are uncommon after abbreviations that contain the first and last letters of the full expression. Examples are: Dr and Mr

In American English, full stops are common, and Mr. and Dr. are preferred.

An abbreviation usually does not have a distinct pronunciation of its own:  we pronounce Mr as ‘mister’ and ‘Dr’ as ‘doctor’. There are, nevertheless, a few exceptions to this rule. For example, the abbreviation p. for pence is sometimes pronounced as ‘pee’.


An acronym is a word constructed from the initial letters of the main words in a phrase.  Examples are: LASER and SCUBA. An acronym can be pronounced as a word and it has the same meaning as the original phrase.

  • SCUBA for Self Contained Underwater Breathing Apparatus
  • LASER for Light Amplification by the Stimulated Emission of Radiation
  • NATO for North Atlantic Treaty Organization
  • Initialism

An intialism is a word constructed from the initial letters of the principal words in a phrase. It is formed in the same way as an acronym but cannot be pronounced as a word. Examples are: BBC for British Broadcasting Corporation and UNO for United Nations Organization.

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