Grammar Abbreviations vs. Acronyms vs. Initialisms |
The Blue Book of Grammar and Punctuation

Abbreviations vs. Acronyms vs. Initialisms

Dictionaries don’t all agree on the definitions of these words and neither do style manuals. So we will attempt to shed more light on the distinctions.

According to, an abbreviation is a shortened or contracted form of a word or phrase, used to represent the whole, as Dr. for Doctor, U.S. for United States, lb. for pound.

Initialisms and acronyms are two types of abbreviations that are used to shorten phrases.

Initialisms are abbreviations that are pronounced one letter at a time.
– BTW (by the way)
Note that most people would simply call these abbreviations, which is fine. Some would call them acronyms, which sticklers would challenge.

Acronyms are abbreviations that are pronounced as words.
– NATO (North Atlantic Treaty Organization)
– AIDS (Acquired Immune Deficiency Syndrome)
– OPEC (Organization of the Petroleum Exporting Countries)
– SPA (Society of Professional Accountants)
– ASAP (as soon as possible)
– Radar (radio detecting and ranging)
– Scuba (self-contained underwater breathing apparatus)

Do you ever wonder about the origin of a word or when it came to be a common part of the language? According to, the word acronym originated in 1943: “As wartime production of names using initials reached an all-time high, it was high time to give a name to the growing arsenal of alphabetic abbreviations. That need was met in a note in the February 1943 issue of American Notes and Queries: ‘Your correspondent who asks about words made up of the initial letters or syllables of other words may be interested in knowing that I have seen such words called by the name acronym, which is useful, and clear to anyone who knows a little Greek.’ ”

“Greek?” Yes, acronym follows the model of other designations for types of words, such as synonym, antonym, and homonym. The -nym means “a kind of word”; acro- means “top, peak, or initial,” as in acrobat or acrophobia.

In step with our observation about differences among dictionaries and style manuals, the Oxford English Dictionary offers two definitions of “acronym”:

  1. A group of initial letters used as an abbreviation for a name or expression, each letter or part being pronounced separately; an initialism (such as ATMTLS). (earliest citation of use 1940)
  2. A word formed from the initial letters of other words or (occasionally) from the initial parts of syllables taken from other words, the whole being pronounced as a single word (such as NATORADA). (earliest citation of use 1943)

As the two diverging definitions suggest, even leading language authorities are not resolute on the subject. While you may continue to come across such variances for acronym and initialism, you can aim for precision within your own understanding and use by applying the differentiations that we’ve discussed.

If the article or the existing discussions do not address a thought or question you have on the subject, please use the "Comment" box at the bottom of this page.

106 responses to “Abbreviations vs. Acronyms vs. Initialisms”

  1. filip says:

    I would like to ask about a difference between compounds and blends (partmanteau words). Is the rule that compounds must be composed of whole words (e.g. fowerpot) and these words can also be written separately or with a hyphen (e.g. flower pot vs. flower-pot); while blends must be composed only of shortened part of words and are always written as one word – not with a hyphen or separately (smog = smoke + fog).

    • A compound word is formed when two or more words are combined to form a new word (such as flowerpot). The English Rules section on “Hyphens” in the Blue Book and our website discusses compound words. According to Rule 1, “To check whether a compound noun is two words, one word, or hyphenated, you may need to look it up in the dictionary. If you can’t find the word in the dictionary, treat the noun as separate words.” There are other rules addressing compound words in that section as well. A portmanteau is a word whose form and meaning are derived from a blending of two or more distinct forms and a portmanteau does not have a hyphen (such as smog).

  2. NKC says:

    Should there be dot(.) after single word?
    Example:1) BMW.
    2) Mercedes.
    Kindly help me.

  3. Martin says:

    Can you address punctuation regarding doctors, dentists, lawyers, public accountants, etc.?

    For example, which of the following is correct (or more widely accepted):

    MD or M.D.

    CPA or C.P.A.

    PhD or Ph.D.

    JD or J.D.

    MS or M.S.

    • You may be disappointed to hear that there is no definitive answer to your question.

      The Chicago Manual of Style
      says, “Use no periods with abbreviations that appear in full capitals, whether two letters or more and even if lowercase letters appear within the abbreviation.” Examples include MD and PhD.

      However, the Associated Press Stylebook says:

      Use periods in most two-letter abbreviations: U.S., U.N., U.K., B.A., B.C.
      Use all caps, but no periods, in longer abbreviations when the individual letters are pronounced: ABC, CIA, FBI

      And this appears in their question and answer forum:
      Q. According to AP style, M.D. and Ph.D. always include periods: Does the same rule apply for JD, Juris Doctor?

      A. AP style is LL.D. for Doctor of Laws, so by that guidance J.D. is correct.

      Q. Why is it M.D. (with periods) but RN (no periods)?

      A. Webster’s abbreviation is RN, though registered nurse should be spelled on first reference in AP stories. M.D. (with periods) is a stylebook exception to Webster’s listing.

      Ph.D., Ph.D.s The preferred form is to say a person holds a doctorate and name the individual’s area of specialty.

      CPA (all caps) is widely used on first reference. If there’s any doubt readers might not know the abbreviation, use the full job title, certified public accountant, in the at some point in the text.

      Master of Arts, Master of Science, Master of Business Administration Abbreviated M.A., M.S., but MBA. A master’s degree or a master’s is acceptable in any reference.

      In cases like these, we recommend choosing your method and staying consistent.

  4. Amy says:

    I’m currently writing my thesis for my PhD (I’m English) and my supervisor is German keeps removing my capitalisations when I define an acronym. For instance, I define Central Nervous System (CNS) in my work for later use as an acronym with capitalisations. He changes it to central nervous system (CNS). Other scientific papers seem to use my method. Would you be able to help me with who is correct here?
    Many thanks,

    • The Chicago Manual of Style’s rule (8.143) says, “Names of diseases, syndromes, diagnostic procedures, anatomical parts, and the like are lowercased, except for proper names forming part of the term. Acronyms and initialisms are capitalized.” Examples:

      acquired immunodeficiency syndrome or AIDS
      computed tomography or CT

      You may also wish to consult either the AMA Manual of Style or Scientific Style and Format.

  5. Richard says:

    I think logic gets overlooked in deciding these matters. ASAP is not a word even if you pronounce it as such cf WASP which is.

    • As our blog states, “ASAP” is not an actual word but an acronym. It is often pronounced as a word. Some people do pronounce it one letter at a time, in which case one could argue that it is an initialism.

  6. Doug says:

    I’ve been listening to sports arguments regarding the initialism RBI v. RBIs. Meaning run batted in. The argument against RBIs is you wouldn’t say run(s) batted ins. I’ve always thought acronyms are the same as words, like FBI you would pluralize it with an s or at least I’ve seen it that way multiple times. Is it the same for RBI?

  7. Abhirup says:

    MOtor Vehicle Emission Simulator (MOVES) -what type is this? As you can see it tales the first 2letters of Motor. Does it qualify as a Mnemonic?

    • A mnemonic is something that helps people remember something (such as a rule or a list of names). We consider MOVES to be an acronym, since it is an abbreviation that is pronounced as a word.

      • TomA says:

        Thanks for this clarification. I was wondering this exact thing about some of these DoD shortenings. (And there are many more in the DoD lexicon.)

        DFAC – Dining Facility
        GeoINT – Geospacial Intelligence
        CONOPS – Concept of Operations

        I should read and treat these like acronyms because they are abbreviations which are pronounced as words. Thanks.

  8. Bruce says:

    I apologise for what is perhaps a trivial question.

    In the case of FBI, I notice it is an abbreviation (Federal Bureau of Investigation) and as such would be written a FBI not an FBI.

    I have a problem with the abbreviation SAP (Systems Applications Products the software company). To me SAP is an abbreviation but according to some people it’s an acronym therefore a company owned by them is referred to as an SAP company not a SAP (clearly one of us is nuts!).

    Q: an SAP (because it’s an acronym – well it isn’t is it) or a SAP (because it’s an abbreviation).

    Please advise, many thanks

    • The Chicago Manual of Style’s rule “An comes before words with a vowel sound,” cites the following examples:

      an LSAT exam room
      an X-Files episode

      It is the initial vowel sound that is important. We recommend “an FBI,” but “a” or “an” before SAP depends on how you want the reader to say it.

  9. Jen says:

    How should acronyms be displayed? I have always written California Alternate Rates for Energy (CARE), but now a co-worker says it should be (“CARE”). Which is correct? Thank you!

  10. Manish says:

    Is WiFi an acronym or Initialism

    • “Wi-Fi” could possibly be considered a type of acronym, although, strictly speaking, it is not an abbreviation for anything. It is a trademark name chosen by the Wi-Fi Alliance for the certification of products that meet certain standards for transmitting data over wireless networks. Some people think that “Wi-Fi” is short for “wireless fidelity,” but it was invented as a play on words with “Hi-Fi.”

      • Natasha says:

        What is the name or word used to describe compound contracted names, for example Washington Mutual = WaMu. It’s not an acronym by definition right?

  11. Marty Alewine says:

    What is the proper use of the words “a” and “an” when used in conjunction with acronyms? There are caases where “a” should be used with the spelled-out version of the pharase while speaking an acronym sounds better using “an.” For example, if I need to write “a” standard operating procedure, I might also need to write “an” SOP. I look forward to your guidance. Thanks!

  12. RandiO says:

    Shouldn’t your abbreviation example of “U.S.” (for United States) really be an initialism?

  13. Irma says:

    I often see “The EU, the ECB and NATO” in one sentence. If institutions need a definite article, why NATO doesn’t?

    • Generally, the is omitted before an acronym. NATO is an acronym ( an initialism pronounced as a word). The others are simply initialisms (pronounced one letter at a time).

  14. Anais says:

    I would like to know what would be the rule for spelling out the full word/sentence next to the acronym/initialism and vice versa. What is the best use: between parentheses or separated by a dash?

    If I take FBI as an example, what would be the correct way:
    FBI (Federal Bureau of Investigation)
    FBI – Federal Bureau of Investigation

    Thanks a lot in advance!!

  15. kicknit1 says:

    When putting states in alphabetical order by their abbreviations, would it be by the full state spelling or the abbreviation. For example would ME for Maine come before MA for Massachusetts? Would DE for Delaware come before D.C. for District of Columbia?

  16. Sling says:

    The domination of LED (light emitting diode) TVs is causing some controversy in the way LED is pronounced. The most common way is to use LED as an abbreviation (‘el’ ‘ee’ ‘dee’) But an increasing proportion of the population are using the acronym ‘lead’. Since most people don’t have a clue what LED stands for, I expect the acronym to take over from the abbreviation in time. After all, nobody pronounces LAN as an abbreviation, nor GIF DOS etc. There is no reason to treat LED any differently.

    • Rich says:

      I have never heard someone pronounce LED TV as “lead TV”, LAN as “el-ahy-en”, or GIF as “gee-eye-eff”.

      Your DOS example is an interesting one though. I have heard it pronounced both ways and I never blink an eye when I hear either one.

      I posted a similar question asking “What determines whether an abbreviation becomes either an initialism or an acronym?”. It seems very arbitrary.

      • Didier says:

        LED is often pronounced as “lead”in non-English spoken countries, just like Wi-Fi isn’t pronounced as waaifaai, but as weefee… (French, Dutch,, … ) One could argue Waai-Fee since Hi-Fi also comes from High-Fidelity (Haai -Fee)
        Personally I find the “weefee” horrible (I’m also a native Dutch speaker) but it would mean one has to say “eePhone” iso aai-Phone, …
        Main reason for the “lead”iso LED is because non-English speakers speaking English don’t realize “lead” has a different meaning. Note also “wee” is used to indicate the letter “W” iso “double U” by some non-English speakers, so www becomes weeweewee iso double U double U double U …
        Interestingly there’s a list of “English”words created by non-English speakers, understood only by non-English speakers ;-)
        We call them Genglish (German-English), Denglish (Dutch-English) or Frenglish (Frensh-English) and I’m sure you can create all other combinations.

  17. Rich says:

    What determines whether an abbreviation becomes either an initialism or an acronym?

    The common thread I see from your post is that if it rolls off the tongue nicely then it’s an acronym and if it doesn’t, it’s an initialism.

    Also if the abbreviation has 3 letters, then it’s an initialism, more than 3 and it’s an acronym.

    • The classification depends on how the word is pronounced rather than how it is spelled. As the post states, “Initialisms are abbreviations that are pronounced one letter at a time,” and “Acronyms are abbreviations that are pronounced as words.” An example of an initialism with more than three letters is NAACP.

  18. oRe says:

    Please, which is correct Dr Olumuyiwa (without period) or Dr. Olumuyiwa (with period)?

  19. Catherine S. says:

    Why is U.S. considered an abbreviation and not an initialism?

  20. Bob Bobson says:

    What about when it is a cross between an initialism and an acronym? For example, JPEG/JPG is pronounced “j-peg”. What then is that?

  21. Fred Whalen says:

    What about LOL, for laughing out loud? Is that an acronym or an initialism? Does it rhyme with “doll”, or is it spelled out L-O-L?

  22. Fred Whalen says:

    Thank you for your opinion on “LOL”, but I think I’ll just continue to be wrong and pronounce it as one word that rhymes with doll.
    I’ll do that for no other reason than to madden the inane people who insist on writing it in otherwise sensible phrases and especially those who write it as a stand-alone statement.

  23. Jasmine L says:

    Thank you for clarifying this! A related question: should “of” be capitalized in an initialism word? For example, is it BOE or BoE for Bank of England?

    • Generally, initialisms are capitalized, but there is no hard-and-fast rule regarding this—at least none that we are aware of.

      • Jasmine L says:

        Thank you, GrammarBook and Fred. It seems that prepositions in initialisms can either be capitalized or not. For example, I found that the Bank of England tends to refer to herself as the BoE while sometimes referred to by others as the BOE.
        Could this be a British versus American English thing (i.e., the British tend not to capitalize prepositions in initialisms whereas the Americans tend to capitalize every letter in initialisms)?

    • Fred Whalen says:

      If you do a Google search of “bank of england” the responses on the first three pages come back with “Bank of England”. The word “of” is not capitalised, so I would guess BoE is the way to go.

  24. Mike says:

    Is there any distinction between acronyms that spell actual words, vs those that don’t? (NATO vs WASP) What about acronyms that spell words incorrectly (MADD Mothers Against Drunk Driving)?

  25. Daniel says:

    What about abbreviating a title in which one of the words is not capitalised? In an organisation i am involved, some individuals serve as members of an “Auxiliary Board” (which is like an advisory committee). These individuals are often called Auxiliary Board members. How would this be correctly abbreviated – ABM or ABm?

  26. James Lindeen says:

    The total number of non-farm workers employed in the United States has been published monthly since 1939. Still reported these days, it is known colloquially as “the monthly jobs report;” but its official title is the “All Employees Total Nonfarm Payrolls.” It is called “PAYEMS” by the Federal Reserve Bank of St. Louis and other agencies. But what is this word PAYEMS? It is neither an acronym nor an initialism. Is it simply a made-up word?

  27. Kathleen says:

    If there is a hyphenated phrase in an initialism, is it necessary to use the hyphen? For example, must Christ-centered Educational Excellence be written as C-cEE or would it be acceptable to be written as CCEE?

  28. Kari says:

    When writing an acronym and including periods after each letter – is it required to put the period after the last letter? I often see this period omitted. It seems like it should be required but I’d be interested in your take on it. Thanks!

  29. Vincent says:

    What standards are we following in writing: AP or the Chicago’s?
    Thanks alot.

    • We provide rules, guidance, and examples based on the recommendations of various authorities on American English grammar and punctuation, including The Chicago Manual of Style, Associated Press Stylebook, Fowler’s Modern English Usage, Bernstein’s The Careful Writer, and many others. Where the authorities differ, we provide options to follow based on the reader’s purpose in writing, with this general advice: be consistent.

  30. KB says:

    In writing legal descriptions, is it proper to have a space between two abbreviated words or not?
    For example W. M. is the abbreviation for Willamette Meridian.
    Which of the following is correct?
    All of Section 16, Township 9 North, Range 27 East, W. M.
    All of Section 16, Township 9 North, Range 27 East, W.M.

  31. D.Scanlon says:

    Is HOMES (Great Lakes) an acronym?

  32. Jon says:

    When creating an acronym that has an compound word such as Homecare in it, should the word be represented by two letters or one in the acronym?

    • Acronym style does not have set rules; rather, it is most often determined by those who are forming the acronym. Most acronyms include one letter per separate word. In your example, “Homecare” is a single compound word and so might often be represented by one letter, the “H.”

  33. Ellen Gibbs says:

    So is there no specific term for the type of abbreviation exemplified by “hazmat,” that is, made up of parts of longer words?

    • The word hazmat is an example of blending, and is known as a portmanteau word. Blending is the formation of a new word with a distinctive meaning by truncating parts of two or more other words.

  34. Clara says:

    What about something like “etc.” for et cetera, and “auto” for automotive? Are these abbreviations only, or could they also be considered acronyms?

    The reason these are differentiated in my mind is that they are shortened words, and not made by the initials of many words put together.

  35. Andrew Dalton says:

    Great distinctions: abbreviations vs. initialisms vs. acronyms! To complete this list, we need one more category. What do we call the following words: ad, con, deli, fan, gym, lab, math, memo, plane, phone, ref, vet? They are words which derive from longer words: advertisement, convict, delicatessen, fanatic, gymnasium, laboratory, mathematics, memorandum, airplane, telephone, referee, veteran (or veterinarian).
    Obviously, they are not initialisms (e.g., FBI, IBM, DVD) because the letters that compose the word are not pronounced one at a time. They are unlike abbreviations (e.g., Dr., lb., U.S.) in that they have no period and are considered complete words in their own right. Finally, they are not exactly like acronyms (e.g. NATO, AIDS, WASP) in that they are not words formed from the initial letters of subsequent parts.

    • Your examples are a type of abbreviation created through truncation. Not all abbreviations use periods. We are not aware of another name for them. We’re trying, but truncaviation seems cumbersome, doesn’t it?

  36. Bryan Dorman says:

    Is there any rule that explains why initialisms such as “CNN” or “CNBC” do not normally take an article? Thank you for your help.

    • There is no particular rule. The abbreviations CNN and CNBC are proper names. Even though they are abbreviations, we refer to them the same way we do Marriott and Microsoft. Whether an article is used generally depends on the sentence. Examples:
      The CNN television channel is owned by Turner Broadcasting System.
      CNN offers 24-hour news coverage.

  37. Ken says:

    Reading hard copy and online British articles recently, it appears that Brits have dropped the period after “Dr,” Mr,” “Mrs” etc. Has that always been the norm, or something new?

    • This is not something new. British usage is no period (known in the UK as a “full stop”) if the abbreviation contains the first and last letters of the abbreviated word.

  38. Eric Wilbanks says:

    An organization I work with has an event called “Youth of the Year.” What would be the proper initialism for that event: YOTY, YOY, YY … or does it not really matter as long as it is consistent?

    • Initialism style does not have set rules; rather, it is most often determined by those who are forming the initialism. Consideration should be given to how the initialism sounds when pronounced and how it looks in writing. As you’re aware from the post, an initialism is an abbreviation that is pronounced one letter at a time. If you settle on YOTY or YOY, you will technically have an acronym because people will naturally want to pronounce it as a word, which is fine too. As you pointed out, consistency is essential.

  39. L. S. McNutt says:

    What about shortening the name of an organization on internal documents?

    Our church is writing a procedures manual. Our official name as it appears on letterhead is the Episcopal Church of the Epiphany.

    We often go by Church of the Epiphany, and then among ourselves just Epiphany.

    All three variations appear in the document. I was thinking the first time the name appears, use the official full name, but then everywhere following, Church of the Epiphany or Epiphany, as long as one is consistently used.

  40. Miranda says:

    Should the “r” in the Abbreviation of “mister” be capitalized? Which is correct Mr. or MR ?
    Should there be a period after the “r” or not?

  41. Tina says:

    Which is correct for a business name?
    Jordan Family Farms
    Is JFF or J.F.F. correct?

    • says:

      Periods are not necessary; however, there are no rules that apply to naming a business or using a shortened version.

  42. Denis Joseph says:

    How is SWOT written? Is it strengths, weaknesses… or Strengths, Weaknesses… In other words, are the initial letters capitalized or not in U.S. English?

  43. rostasi says:

    What do you call a word that sounds like the initials of something else?
    For example: “Arby’s” (there’s some disagreement on whether it really stands for “roast beef”).

    • says:

      Perhaps it could qualify as a homonym. The words sounds/is pronounced the same, but it stands for something else: Arby’s and R.B.’s.

  44. shonagh clark says:

    What are the initials for a hyphenated word sub-annual as in sub-annual financial collection?

  45. Mitchell Golomb says:

    I didn’t see all the questions, but what would you call cpap? The first word is pronounced and the rest are sn acronym.

  46. Kallie says:

    When writing out the initialism is the noun supposed to be capitalized or not?
    For example: emergency department (ED) or Emergency Department (ED); police department (PD) or Police Department

    Obviously, if it is a proper noun it is capitalized but if the noun is not proper?

    • says:

      If you are not writing about a specific department such as “UCLA Medical Center Emergency Department” or “New York Police Department,” do not capitalize.

      Our emergency department (ED) is not busy today.
      The police department (PD) has been issuing lots of tickets this week.

      Unless there’s a good reason to initialize, such as avoiding full references numerous times in a short space, including the initialism after a general department reference typicallly isn’t necessary.

  47. Kristi Millburn says:

    What a terrific blog. I’ve learned so much from reading it. Thank you for all your insights and knowledge.

  48. 753BC says:

    I’m an ESL student and right now I’m in the process of writing a term paper on the use of shortened words on the Internet (specifically on different social networks like Twitter). It’s not easy to do, to be honest, because there are so many peculiarities to take into account. Abbreviations are just part of the whole, and dividing them into only two big groups is not enough, in my opinion. There are also such cases when one part of an abbreviation is pronounced as an initialism, and the other part is pronounced as an acronym: CD-ROM. There are abbreviations in which the first part consists of only one letter and the other part is a whole word: E-mail, A-bomb, etc. In addition to that, there are words that have numbers instead of syllables or words: B2B – business-to-business, 2g4u – too good for you, l8r – later, etc. I don’t think we can consider such examples as abbreviations, so we have to think of some other group for these words. As far as I know, they’re called letter/number homophones.
    Furthermore, I can’t agree with on considering lb., Dr., Mr., and similar examples to be abbreviations. We don’t pronounce them letter-by-letter, nor do we pronounce them as whole words => they’re neither initialisms nor acronyms. They’re just graphical shortenings that exist only in written form.
    There are also clipped words, blends, etc., which are not abbreviations, of course. I just wanted to mention that they exist.
    All in all, this topic is really interesting, but, at the same time, challenging.

  49. Stacey Bouchet says:

    I just discovered this site tonight around 11pm-midnight. It is 5 a.m. now, and I have not left my MacBook this entire time because I am completely 100% addicted to what you’re sharing! It is fascinating! Thank you, seriously.

  50. Graham Skells says:

    Here in Canada we follow many British practices in English, such as spellings involving “or” vs “our” (labour vs. labor, colour vs. color). In fact as I type them, your web page is flagging the “-our” words as spelling errors. But one thing that doesn’t happen here is the British omission of a period in abbreviations that use the same first and last letters as the words of which they are abbreviations. Here we follow the American (or as we would more often say, “the U.S.”) practice (Mr. rather than Mr).

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