Let’s be honest. You’ve probably used the word “acronym” to describe something that wasn’t actually an acronym. Most people have. And nobody corrected you because, frankly, most people don’t know the difference either.
The terms abbreviation, acronym and initialism get thrown around interchangeably in everyday conversation, in classrooms, in offices, even in published content. And every time they’re used incorrectly, something small but significant happens. The writing loses a sliver of precision. The reader senses something is slightly off. And the writer’s credibility takes a quiet hit they probably never even notice.
It sounds like a small problem. But small problems have a way of compounding. If you’re a student working on a thesis, the wrong punctuation on an abbreviation can trigger a style guide violation. If you’re an editor reviewing a manuscript for professional editing, inconsistent usage across a document creates hours of unnecessary cleanup. If you’re a content creator trying to build authority, misidentifying an initialism as an acronym signals to your more informed readers that you haven’t quite done your homework.
The confusion is understandable. These three categories overlap in places, and the terminology itself can feel unnecessarily academic. But once you understand the distinctions, and they’re genuinely not complicated, everything clicks into place. You stop second-guessing yourself. You stop Googling “is FBI an acronym” for the fourth time this year. And your writing becomes noticeably sharper.
That’s exactly what this guide is built to do. We’re going to walk through clear definitions, practical rules, real-world examples and the kind of expert-level detail that turns uncertainty into confidence. Whether you’re writing a blog post, formatting a research paper or putting together a book manuscript, by the end of this you’ll know precisely what you’re dealing with and how to handle it correctly every single time.
No jargon for the sake of jargon. No unnecessary complexity. Just a clear, practical breakdown you can actually use.
Before we get into the distinctions between acronyms and initialisms, we need to start with the umbrella term that covers them both. And that’s the abbreviation.
An abbreviation, at its core, is simply a shortened form of a word or phrase. That’s it. It’s the broad category. When you write “Dr.” instead of “Doctor” or “etc.” instead of “et cetera,” you’re using an abbreviation. The original word gets trimmed down, and the shortened version stands in its place.
What makes abbreviations interesting, and occasionally tricky, is that they come in several different forms. Not all abbreviations work the same way, and recognising the type you’re dealing with helps you punctuate and format it correctly.
Contractions are one of the most common types. These are abbreviations where letters from the middle of a word are removed, but the first and last letters remain. Think “Mr.” for “Mister” or “Dr.” for “Doctor.” In British and Australian English, there’s actually a convention where contractions that end with the same letter as the full word don’t require a full stop. So you’ll often see “Mr” and “Dr” without periods in AU English, while American English almost always includes them.
Truncations are abbreviations where the word is simply cut short. “Prof.” for “Professor,” “etc.” for “et cetera,” “e.g.” for “exempli gratia.” These almost always take a full stop because the word has been visibly chopped, and the period signals that something is missing.
Then there are symbols and measurement abbreviations. The ampersand (&), the at symbol (@), and units like “kg,” “cm” and “ft” all fall under this umbrella. In scientific and technical writing, measurement abbreviations typically drop the full stop entirely, which is worth knowing if you’re working across different contexts.
The linguistic reason behind all of this is straightforward. Language naturally gravitates towards efficiency. We shorten things because it saves time, saves space and when done properly, doesn’t sacrifice meaning. The challenge is that “properly” looks different depending on the type of abbreviation, the style guide you’re following and the audience you’re writing for.
And that brings us to punctuation, which is where a lot of writers start to stumble.
The honest answer is that punctuation rules for abbreviations are not universal. They depend on the style guide, the regional convention and sometimes the specific word itself. “U.S.” with periods is standard in many American contexts, while “US” without periods is preferred in most Australian and British publications. Both are correct, but using them inconsistently within the same document is not.
The golden rule? Pick a convention and stick to it. Consistency is more important than which specific rule you follow, as long as that rule comes from a credible source.
Now we’re getting into the territory where confusion really starts to build. Because acronyms are technically a type of abbreviation, but they behave very differently from the examples we just covered.
An acronym is an abbreviation formed from the initial letters of a phrase, and here’s the crucial part: it’s pronounced as a word. That pronunciation element is what separates an acronym from everything else.
NASA is an acronym. You say it as “nah-sah,” not “N-A-S-A.” NATO is an acronym. SCUBA is an acronym. RADAR is an acronym. In every case, the letters come together to form something that sounds and functions like a standalone word.
This is why some acronyms eventually lose their capitalisation entirely. “Radar” started as RADAR (Radio Detection and Ranging). “Scuba” started as SCUBA (Self-Contained Underwater Breathing Apparatus). Over time, as these words became so embedded in everyday language that people forgot they were acronyms at all, they transitioned to lowercase. It’s a natural part of how language evolves.
The pronunciation test is the simplest way to identify an acronym. If you can say it as a word, it’s an acronym. If you find yourself spelling out each letter individually, it’s not. That distinction might sound basic, but it’s the exact point where most people’s understanding breaks down, because they assume anything made from initial letters is automatically an acronym. It isn’t.
Acronyms appear across virtually every field. Government agencies love them. NASA, NATO, ASIO. Science relies on them. LASER (Light Amplification by Stimulated Emission of Radiation) is one most people don’t even realise is an acronym. Organisations use them constantly. UNESCO, QANTAS, ANZAC. The key thread connecting all of these is that they’re spoken as words, not spelled out letter by letter.
One more thing worth noting. Acronyms generally don’t use periods between the letters. You won’t see “N.A.S.A.” in modern writing. The trend across all major style guides has moved firmly towards clean, period-free formatting for acronyms.
Here’s where the real distinction lives, and it’s the one most people miss entirely.
An initialism, like an acronym, is formed from the initial letters of a phrase. But unlike an acronym, it’s pronounced letter by letter. You don’t say “fbi” as a word. You say “F-B-I.” Each letter gets its own individual articulation.
FBI. CIA. USA. BBC. CEO. PhD. ATM. These are all initialisms, not acronyms, despite the fact that nearly everyone calls them acronyms in casual conversation. And while nobody is going to pull you aside at a dinner party for getting it wrong, if you’re writing professionally, editing someone else’s work or studying language at any serious level, the distinction matters.
Initialisms are almost always written in capital letters and almost never use periods between the letters in modern Australian and British English. “FBI” is standard. “F.B.I.” feels dated, though you’ll still encounter it occasionally in American publications that follow older conventions.
The overlap between acronyms and initialisms is where things get genuinely interesting. Consider “ASAP.” Some people pronounce it as a word (“ay-sap”), which would make it an acronym. Others spell it out (“A-S-A-P”), which would make it an initialism. Context, audience and even regional habits can shift how a term is classified, and that’s perfectly normal. Language isn’t always neat, and acknowledging the grey areas is part of understanding how it actually works.
It’s also worth paying attention to how abbreviation, acronym and initialism relate to professional titles and degrees. “Dr.” is an abbreviation. “PhD” is an initialism. Both relate to academic credentials, but they’re categorised differently because they behave differently. If you’re working on a document that uses both, understanding this distinction helps you format them correctly and consistently.
At this point, you’ve got the individual definitions. Now let’s put them side by side so the contrasts are crystal clear.
The three core differences come down to pronunciation, formation and formatting.
Pronunciation is the big one. An abbreviation is a shortened form of a single word, and when you encounter it in text, you typically read the full word in your head. You see “Dr.” and your brain reads “Doctor.” An acronym is formed from initial letters and pronounced as a word. You see “NASA” and say “nasa.” An initialism is also formed from initial letters but is pronounced letter by letter. You see “FBI” and say “F-B-I.”
Formation differs too. Abbreviations can be formed from any part of a word, the beginning, end, middle or a combination. Acronyms and initialisms are both formed exclusively from the first letters of each word in a phrase.
Formatting follows patterns but isn’t entirely rigid. Abbreviations often use periods in American English and less frequently in Australian English. Acronyms almost never use periods. Initialisms generally don’t either, though older style conventions sometimes include them.
| Feature | Abbreviation | Acronym | Initialism |
| How it is formed | Can use part of a word (beginning, middle, or end) | Formed from first letters of a phrase | Formed from first letters of a phrase |
| Pronunciation | Full word is read (mentally expanded) | Pronounced as a single word | Pronounced letter by letter |
| Example | Dr. → Doctor, approx. → approximately | NASA, UNESCO, NATO | FBI, BBC, USA |
| How it is said | Spoken as the full form | Spoken as a word (e.g., “nasa”) | Spoken as individual letters (e.g., “F-B-I”) |
| Use of periods | Often uses periods (esp. in American English) | Rarely uses periods | Usually no periods |
| Typical structure | Flexible (not strictly initial letters) | Strictly initial letters | Strictly initial letters |
The overlaps are real, and pretending they don’t exist would be dishonest. “ASAP” lives in a grey zone. So does “FAQ,” which some people pronounce as “fak” and others spell out as “F-A-Q.” These ambiguities don’t undermine the categories. They simply reflect the fact that living language doesn’t always conform perfectly to classification systems. The categories are still useful, overwhelmingly so, but flexibility matters at the edges.
Sometimes the fastest way to identify what you’re dealing with is to run it through a quick mental checklist. Here’s a simple decision process that works every time.
First, ask yourself: does this represent a shortened form of a single word? If the answer is yes, you’re looking at an abbreviation. “Dr.” is a shortened form of “Doctor.” “Prof.” is a shortened form of “Professor.” Simple.
If the answer is no, and the short form is made up of the initial letters from multiple words, move to the next question.
Can you pronounce it as a word? If yes, it’s an acronym. NASA, NATO, ANZAC, SCUBA. They all roll off the tongue as single words.
If you can’t pronounce it as a word and instead find yourself saying each letter individually, it’s an initialism. FBI, CEO, ATM, BBC.
That’s genuinely all there is to it. Three questions, three clear outcomes. Print it, stick it on your desk, and never second-guess yourself again.
Rules for Correct Usage: Capitalisation, Punctuation and Pluralisation
Knowing what something is matters. Knowing how to use it correctly matters more. Let’s get into the practical rules.
Capitalisation varies by type. Abbreviations don’t follow a single capitalisation rule. “Dr.” is capitalised because it’s derived from a proper title, but “etc.” stays lowercase because it’s derived from a common phrase. Acronyms are typically written in all capitals, though as we discussed, some become lowercase over time as they’re absorbed into everyday vocabulary. Initialisms are almost always written in capitals.
The most important rule here isn’t which convention you choose. It’s that you stay consistent. If you write “NASA” on page three and “Nasa” on page twelve, you’ve created an inconsistency that any careful reader or editor will notice. Consistency signals professionalism. Inconsistency signals carelessness.
Punctuation rules centre primarily around periods. In Australian English, the trend has moved strongly towards omitting periods from acronyms and initialisms. “US” rather than “U.S.” “PhD” rather than “Ph.D.” Abbreviations that are truncations still tend to keep their periods (“etc.,” “e.g.,” “Prof.”), while contractions that end with the same letter as the full word often drop them (“Mr,” “Dr”).
Commas and other punctuation marks interact with short forms the same way they interact with regular words. If the abbreviation falls at the end of a sentence that would normally end with a full stop, and the abbreviation already has a period, you don’t double up. One period does the job of both.
Pluralisation is simpler than most people think. To make an acronym or initialism plural, just add a lowercase “s.” CDs, FAQs, PhDs, URLs. No apostrophe. The apostrophe-for-plurals mistake (“CD’s,” “FAQ’s”) is one of the most common errors in written English, and it’s one that every style guide explicitly warns against. Apostrophes indicate possession, not plurality. “The CEO’s decision” is correct because the decision belongs to the CEO. “Multiple CEOs attended” is correct because you’re simply indicating more than one.
This is one of those rules that seems obvious once you hear it but gets ignored with remarkable frequency.
The DoFU principle is straightforward: the first time you use an abbreviation, acronym or initialism in a document, spell out the full term and place the short form in parentheses immediately after. Every subsequent use can then use the short form alone.
“The National Aeronautics and Space Administration (NASA) announced a new mission.” From that point on, “NASA” is all you need.
“The Federal Bureau of Investigation (FBI) launched an inquiry into the matter.” After that introduction, “FBI” carries itself.
The rationale is pure reader-friendliness. You can never assume that every reader knows what every short form stands for. Even common ones. Especially in formal writing, academic papers, business reports and published books, the DoFU principle isn’t optional. It’s expected.
There are exceptions, but they’re narrow. Terms that are so universally recognised that spelling them out would feel patronising, like “ATM” or “TV,” can sometimes skip the first-use definition. But even here, context matters. If you’re writing for a highly specialised audience and you’re confident they know the term, you have more flexibility. If there’s any doubt, define it. The cost of defining something your reader already knows is minimal. The cost of not defining something they don’t know is confusion.
When you’re working on long-form content like a book manuscript, especially if you’re collaborating with a ghostwriting service, establishing a clear shorthand glossary early saves enormous amounts of time during revisions.
Knowing the rules is one thing. Knowing when to apply them wisely is another.
Short forms exist to improve efficiency. If a term appears repeatedly throughout a document, using its abbreviated form after the first introduction makes the text leaner and faster to read. But if a term only appears once or twice, abbreviating it actually adds cognitive load. The reader has to remember what the short form stands for without enough repetition to make it stick.
The balance between efficiency and clarity shifts depending on your format. In formal academic writing, you follow the style guide’s rules to the letter. In informal content, like blog posts or marketing copy, you have more freedom, but clarity should still come first. Nobody wants to read a paragraph stuffed with so many initialisms that it reads like a government memo.
Different professional fields have their own conventions too. Scientific and medical writing uses standardised abbreviations without periods, and readers in those fields expect them. Legal writing leans heavily on Latin abbreviations and has its own formatting traditions. Technical documentation prioritises consistency above all else and often includes a dedicated glossary at the front of the document.
If you’re involved in publishing, whether through book design or manuscript preparation, understanding how abbreviations function across these different contexts helps you produce documents that feel polished and genre-appropriate.
The readability factor is worth emphasising. A paragraph with three or four short forms in it is manageable. A paragraph with eight or nine becomes exhausting. When in doubt, use fewer. Your readers will thank you.
If you’re writing in any professional or academic context, a style guide isn’t a suggestion. It’s the authority. And different guides handle abbreviations, acronyms and initialisms in slightly different ways.
The four major guides most writers encounter are APA (Publication Manual of the American Psychological Association), MLA (Modern Language Association Handbook), the Chicago Manual of Style and the AP Stylebook (Associated Press). Each has its own perspective on when to abbreviate, how to punctuate and when the DoFU principle applies.
| Feature | APA (7th ed.) | MLA (9th ed.) | Chicago Manual of Style | AP Stylebook |
| General approach | Formal, clarity-focused; defines before use | Moderately flexible; clarity for academic readers | Highly flexible; allows both formal and traditional usage | Concise, journalism-focused; readability |
| First use rule | Spell out full term first, then abbreviation in brackets | Spell out first unless widely known (e.g.DNA) | Spell out first; abbreviation optional if well known | Spell out first unless extremely common (e.g.FBI, NASA) |
| Acronyms (pronounced as words) | Allowed after definition (e.g. WHO) | Allowed if widely recognised | Allowed freely if context supports | Allowed if widely recognised and familiar to general audience |
| Initialisms (letter-by-letter) | Always define first | Define first unless universally known | Define first; may omit for very common ones | Often used without definition if widely known |
| Punctuation in abbreviations | Generally no periods (e.g. USA) | No periods in most cases | No periods for abbreviations and acronyms | No periods in abbreviations (e.g. USA,BBC) |
| Capitalisation rules | Capitals for standard acronyms/initialisms | Same as APA | Flexible; depends on term usage | Capitals preferred for clarity in news writing |
| Common philosophy | Precision and academic clarity | Reader comprehension in humanities | Historical + stylistic balance | Speed, clarity and brevity for journalism |
The common ground across all four is significant. They all endorse the DoFU principle for less common terms. They all prefer consistency within a document. They all discourage unnecessary abbreviation when the full term would serve better.
Where they diverge is in the details. APA uses periods for “U.S.” when it functions as an adjective but not for state abbreviations. Chicago follows a similar pattern for “U.S.” and adds periods to “A.M.” and “P.M.” AP uses periods for “U.S.,” “U.N.” and courtesy titles like “Dr.” and “Mr.” MLA generally avoids periods for common initialisms.
The takeaway is simple: know which guide applies to your context and follow it. If you’re writing an academic paper, check your institution’s requirements. If you’re preparing a manuscript for publishing, ask your editor or publisher which convention they follow. If you’re writing content for a business, establish an internal style sheet and make sure everyone sticks to it.
Even experienced writers trip up on short forms. Here are the errors that come up most frequently, and how to sidestep them.
Incorrect punctuation tops the list. Using “U.S.” in one paragraph and “US” in the next. Adding periods to acronyms that don’t need them. Forgetting them on truncations that do. The fix is simple but requires discipline: decide on your convention before you start writing and apply it consistently throughout.
Apostrophe misuse for plurals is epidemic. “DVD’s” instead of “DVDs.” “CEO’s” instead of “CEOs.” Unless you’re showing possession, the apostrophe has no business being there. This is one of the most common errors that professional editing catches during manuscript review.
Inconsistent capitalisation creates a jarring reading experience. “NATO” on one page and “Nato” on the next. “PhD” in one section and “PHD” in another. Pick a format and don’t deviate.
Misidentifying the type of short form might not seem like a big deal, but it can lead to pronunciation cues that confuse readers. If a style guide asks you to differentiate between acronyms and initialisms in a glossary, getting the classification wrong undermines the document’s accuracy.
Overuse is perhaps the most damaging mistake because it affects the reader’s entire experience. A text crammed with short forms feels dense, impersonal and difficult to follow. Use abbreviations to serve your reader, not to show off how many you know.
And finally, failing to define on first use. It happens constantly, especially in drafts where the writer is so familiar with their subject matter that they forget the reader might not be. Always define. Always.
The best safeguard against all of these errors is a dedicated proofreading pass focused specifically on short forms. Go through your document once just looking at abbreviations, acronyms and initialisms. Check for consistency, correct punctuation, proper pluralisation and first-use definitions. It takes fifteen minutes and catches problems that a general read-through almost always misses.
There are a handful of myths about abbreviations that persist despite being flatly incorrect. Let’s clear them up.
Myth: All abbreviations end with a period.
Reality: They don’t. Acronyms and initialisms in modern usage rarely use periods. Measurement abbreviations in scientific contexts almost never do. And in Australian and British English, contractions that end with the same letter as the full word often skip the period entirely.
Myth: You always use an apostrophe when pluralising short forms.
Reality: You almost never should. “DVDs” is correct. “DVD’s” is not, unless the DVD possesses something. Every major style guide is clear on this point.
Myth: Acronyms and initialisms are the same thing.
Reality: They share a formation method but differ fundamentally in pronunciation. Acronyms are pronounced as words. Initialisms are spelled out letter by letter. The distinction is real, meaningful and worth getting right.
Myth: You don’t need to spell out universally known short forms on first use.
Reality: “Universally known” is more subjective than most writers realise. What’s obvious to you might be unfamiliar to a reader from a different background, profession or generation. Formal writing advises DoFU in nearly all cases, and even informal writing benefits from erring on the side of clarity. Understanding how to copyright a book, for example, involves knowing that seemingly universal terms like “IP” still need context in certain documents.
Here’s a quick self-check. Run through these and see how you go.
Is “NASA” an acronym, initialism or abbreviation? It’s an acronym. You pronounce it as a word.
What about “FBI”? That’s an initialism. You say each letter individually.
How do you pluralise “FAQ”? You write “FAQs.” No apostrophe.
,Should you write “U.S.” or “US” in an Australian publication? Generally “US” without periods, following AU English conventions. But always check your specific style guide.
Is “Dr.” an abbreviation, acronym or initialism? It’s an abbreviation, specifically a contraction.
If you got all five right, you’ve properly absorbed the core concepts. If you missed one or two, no stress. Go back and revisit the relevant section. The goal isn’t perfection on the first pass. It’s building a reliable understanding you can apply every time you write.
When you’re putting together any serious written project, whether it’s a blog, a report or a full manuscript, this kind of foundational knowledge makes the difference between content that reads as polished and content that reads as almost there. It’s a similar principle to understanding the distinction between endorse vs approve in professional communication. Precision in language builds trust with your reader.
Let’s bring it all together.
An abbreviation is the broad category. It’s any shortened form of a word or phrase. “Dr.,” “etc.,” “Prof.” are all abbreviations.
An acronym is a specific type of abbreviation formed from initial letters and pronounced as a word. NASA, NATO, SCUBA.
An initialism is also formed from initial letters but pronounced letter by letter. FBI, CEO, PhD.
The differences come down to pronunciation and, to a lesser extent, formatting conventions. The rules for using them correctly come down to consistency, proper punctuation, correct pluralisation and the DoFU principle.
None of this is complicated once you’ve seen it laid out clearly. And the payoff for getting it right is real. Your writing becomes more precise. Your documents become more professional. Your credibility as a communicator goes up. Whether you’re drafting a blog post, preparing a manuscript for marketing, or writing academic research, these are the small details that separate good writing from excellent writing.
If you’re working on a book or any long-form written project, getting the fundamentals right from the start saves you enormous time during editing and revision. At Melbourne Print and Publish, the focus is always on helping writers produce work that meets the highest professional standards, and mastering these foundational elements is part of that journey.
Precision in language isn’t about being pedantic. It’s about respecting your reader enough to communicate clearly. And that’s always worth the effort.
An abbreviation is a shortened form of a word or phrase. It includes contractions like "Mr." and "Dr.," truncations like "etc." and "Prof.," and extends to symbols and measurement units. It's the umbrella term that covers all types of shortened forms in writing.
An abbreviation is the general category for any shortened form. An acronym is a specific type of abbreviation that's formed from the initial letters of a phrase and pronounced as a single word, like NASA or SCUBA. Not all abbreviations are acronyms, but all acronyms are abbreviations.
An initialism is formed from the initial letters of a phrase, just like an acronym, but it's pronounced letter by letter rather than as a word. FBI, CIA, CEO and PhD are all initialisms.
The approach depends on the type of abbreviation. For contractions, you remove middle letters and often keep the first and last. For truncations, you cut the word short and add a period. For acronyms and initialisms, you take the first letter of each word in the phrase. Always check a style guide relevant to your context.
Use them when a term appears frequently after its first definition, to improve readability and reduce unnecessary repetition. Avoid them when a term only appears once or twice, or when the full word would provide greater clarity or impact.
Common abbreviations include "Dr." (Doctor), "etc." (et cetera), "e.g." (for example), "Prof." (Professor), "Mr." (Mister) and "Blvd." (Boulevard). Measurement abbreviations like "kg," "cm" and "ft" also fall into this category.
The difference is pronunciation. Acronyms are pronounced as words (NASA, NATO). Initialisms are pronounced letter by letter (FBI, BBC). Both are formed from initial letters, but how you say them determines which category they belong to.
An acronym is a type of abbreviation, but not all abbreviations are acronyms. The term "abbreviation" covers any shortened form of a word or phrase, while "acronym" specifically refers to initial-letter formations that are pronounced as words.
It depends on the type. Contractions remove interior letters (Doctor becomes Dr.). Truncations cut a word short (Professor becomes Prof.). Acronyms and initialisms take the first letter of each word in a multi-word phrase.
Spell out the full term on first use with the short form in parentheses. Maintain consistent capitalisation and punctuation throughout. Pluralise by adding a lowercase "s" without an apostrophe. Follow the specific style guide required for your context.
Yes, but with conditions. Most academic style guides require the DoFU principle and recommend using abbreviations sparingly. The APA, MLA, Chicago and AP guides all have specific rules for how abbreviations should be handled in scholarly work.
Truncations typically take a period (etc., Prof.). Contractions in AU English often drop the period when the last letter matches the full word (Mr, Dr). Acronyms and initialisms generally don't use periods in modern usage. Always follow your applicable style guide.
Not always. In Australian English, many abbreviations, particularly acronyms and initialisms, are written without full stops. Truncations usually keep them. The convention varies by style guide and regional preference.
The word "abbreviation" itself is not an abbreviated form of another word. It comes from the Latin "abbreviare," meaning "to shorten." It's sometimes informally shortened to "abbrev." or "abbr."
They improve efficiency in communication by reducing word count and saving space without sacrificing meaning. In technical, scientific and professional writing, they allow frequently referenced terms to be expressed concisely after their initial definition.
The main types are contractions (Mr., Dr.), truncations (Prof., etc.), acronyms (NASA, NATO), initialisms (FBI, CEO), symbols (&, @) and measurement abbreviations (kg, cm). Each type has its own formatting and punctuation conventions.
It's called an abbreviation. If the shortened form is made from the initial letters of multiple words and pronounced as a word, it's an acronym. If pronounced letter by letter, it's an initialism.
Write them in capital letters without periods (NASA, not N.A.S.A.). Spell out the full term on first use with the acronym in parentheses. Use the acronym alone for all subsequent references. Pluralise by adding a lowercase "s" (NASAs, though this is rarely needed).
The plural is "abbreviations." For pluralising specific abbreviated terms, add a lowercase "s" without an apostrophe. CDs, FAQs, PhDs, URLs. Never use an apostrophe for plurals of short forms unless indicating possession.
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