Acronyms and initialisms: A user's guide

There’s a lot of confusion when it comes to acronyms and initialisms. Some writers provide definitions every time they use them, while others don't. But which is best practice? And what’s the difference between acronyms and initialisms anyway? In this post, I’ll set the record straight so you can refer to these abbreviations correctly and use them intentionally and effectively in your writing.

What is an acronym?

An acronym is an abbreviation of an expression or name where the first letters create a new word. Here are some common examples:

• ASIO (Australian Security Intelligence Organisation)

• BOM (Bureau of Meteorology)

• FOMO (fear of missing out)

• GIF (graphics interchange format)

• NASA (National Aeronautics and Space Administration)

• NATO (North Atlantic Treaty Organization)

• PIN (personal identification number)

• RAT (rapid antigen test)

• SARS (severe acute respiratory syndrome)

• TAFE (technical and further education)

• UNESCO (United Nations Educational, Scientific and Cultural Organization)

• WHO (World Health Organization)

Note: The word ‘acronym’ is sometimes used to refer to abbreviations that are either acronyms or initialisms. While this isn’t technically correct, more people are familiar with this word, so if you’re working with colleagues or authors who don’t know the terminology, feel free to use ‘acronym’ as a broad term for both.

What is an initialism?

An initialism is an abbreviation of an expression or name where each letter is pronounced separately. Here are some common examples:

• ABC (Australian Broadcasting Corporation)

• CEO (chief executive officer)

• CSIRO (Commonwealth Scientific and Industrial Research Organisation)

• DVD (digital video disc)

• FBI (Federal Bureau of Investigation)

• GST (goods and services tax)

• HR (human resources)

• IBS (irritable bowel syndrome)

• PDF (portable document format)

• PR (public relations)

• PTSD (post-traumatic stress disorder)

• UK (United Kingdom)

When should you define them?

Typically, you define an acronym or initialism at first mention, right after the expanded form. Any subsequent mentions take the abbreviated form. For example:

• The Australian Labor Party (ALP) was founded in 1901. Even though the ALP has a long history …

  
  

• According to the Bureau of Meteorology (BOM), Cyclone Tina will hit the eastern seaboard on Sunday. The BOM gave no further details about …

  
  

• A self-managed super fund (SMSF) can give you more control over your money. However, when you switch to an SMSF ...

That said, if you’re working on a long document and an unusual acronym is used frequently in chapter 1 and then again in chapter 7, define it anew in case readers have forgotten what it means.

If an acronym is only used a couple of times in a document, consider deleting it and using the expanded form on its own for simplicity and clarity, particularly if you’re writing for a general audience. (For more on how to make your writing more user-friendly, see The curse of knowledge: How to write for readers who aren’t experts.)

On the other hand, if an abbreviation is widely known, you don’t need to define it. For example, most readers are familiar with AIDS, JFK, KPI, NASA, PIN, RSVP and VIP.

How do you make them plural?

To make acronyms and initialisms plural, you add a lowercase ‘s’ at the end. For example, ‘CEOs’ and ‘GIFs’. According to the Australian Government Style Guide, it’s best to avoid plurals on first use to avoid confusion. Try to rephrase the sentence so the singular form is used. The same applies to possessives.

What about abbreviations that combine both?

Some abbreviations are a blend of both acronyms and initialisms. (Isn’t English a joy?) In other words, one letter is spelled out and the rest of the letters are pronounced like a full word. For example:

• CPAP (c-pap)

• DFAT (d-fat)

• IPEd (i-ped)

• JPEG (j-peg)

• MCAT (m-cat)

Are acronyms and initialisms always capitalised?

Acronyms or initialisms are usually – but not always – fully capitalised, so check your source, dictionary or style guide. For example, FYI/fyi, ASAP/asap, AKA/aka and FOMO/fomo are all acceptable, depending on your dictionary, preference or audience.

Some organisations like to throw in a solitary lowercase letter for differentiation (like 'MoMA'), or because it’s a shortened form of another word (‘Ed’ in ‘IPEd’ is short for ‘Editors’).

Many acronyms and initialisms have entered common usage and are spelled in lowercase letters and pronounced as words. What’s more, they are rarely defined. Here are some examples:

• Anzac (Australia and New Zealand Army Corps)

• Gestapo (Geheime Staatspolizei)

• Interpol (The International Criminal Police Organization)

• laser (light amplification by stimulated emission of radiation)

• modem (modulator-demodulator)

• Qantas (Queensland and Northern Territory Aerial Service)

• radar (radio detecting and ranging)

Note: Just because the acronym or initialism is in all caps doesn’t mean the expanded form should be (unless it’s a proper noun). For example, ‘enduring power of attorney’ doesn’t take capitals according to the Macquarie Dictionary, even though its initialism (‘EPOA’) does. That said, some in-house style guides prefer to capitalise legal terms or documents, so make sure you check.  

Should you use full stops in acronyms and initialisms?

Typically, acronyms and initialisms don’t take full stops. However, check your style guide to make sure. Some publications or businesses like to add full stops in certain abbreviations, such as ‘U.S.’ or ‘a.k.a’.

Can you overuse acronyms and initialisms?

Yes, using too many abbreviations can weigh down your sentences and affect readability. (Some people call it 'alphabet soup' – and I can understand why!) Even if you defined them early, it’s hard for readers to remember what they all mean, particularly if they’re uncommon or used sporadically. To avoid this, minimise acronyms or initialisms, use the expanded forms for clarity and rewrite a sentence if it contains more than three acronyms/initialisms.

What are common pitfalls?

Below are some common errors I see when people use acronyms or initialisms:

• Repeating the last word in the acronym or initialism. For example, ‘PIN number’, ‘RAT test’, ‘SEO optimisation’, 'HIV virus' or ‘ATM machine’. This is a tautology – unnecessary repetition – so watch out for it.

  
  

• Changing the spelling of an expanded acronym/initialism to reflect local usage. For example, if you’re in Australia, don’t change the ‘z’ in ‘World Health Organization’, even though -ise is preferred usage in that region. Keep the original spelling.

  
  

• Using the incorrect plural form. For example, ‘call to action (CTA)’ becomes ‘calls to action’ in the expanded form (not 'call to actions') and ‘CTAs’ in the abbreviated form.

  
  

• Not defining an acronym/initialism that refers to different organisations. For example, 'CIA' is a well-known abbreviation and may not need defining, but it doesn't just refer to the 'Central Intelligence Agency'. It's also the initialism for the 'Canadian Institute of Actuaries', the 'Chemical Institute of Australia' and the 'American Culinary Institute'. Define it at first mention so there's no confusion.

Final thoughts: Acronyms and initialisms

Acronyms and initialisms are both abbreviations, but with one key difference: the first is pronounced like a new word and the second is spelled out letter by letter. (That said, you can still use the word ‘acronym’ as a blanket term for both.)

When you’re writing, make sure you define them at first use, or if you’d like to make your writing more user-friendly, minimise usage or opt for the expanded forms. And don’t forget to check your dictionary or style guide for correct capitalisations and punctuation.

Need help navigating abbreviations? Or maybe you’ve got a manuscript ready for editing? Either way, get in touch through my contact form or request a sample edit.