The Difference Between an Acronym and an Initialism

Now You KnowYou should know the difference between an acronym and an initialism.

Both acronyms and initialisms are abbreviations, but there is a key difference between the two, at least at present. Due to rampant misuse of the term “acronym” some dictionaries are now starting to add an extra definition to it, allowing acronyms to expand their scope to include initialisms.  So as the English language evolves, this additional definition of acronym may stick and become widely accepted. But at present, it’s generally still good form to distinguish between the two.

Acronyms, of course, are abbreviations where the abbreviation is formed from letters of other words (usually the first letter of each word, though not always).  The part of the definition of acronym that many people miss is that the resulting abbreviation needs to be pronounceable as a word.  Examples of this would be things like RAM (Random Access Memory); LASER (Light Amplification by Stimulated Emission of Radiation); NASA (National Aeronautics and Space Administration), and OPEC (Organization of Petroleum Exporting Countries).

Initialisms are very similar to acronyms in that they are made up of letters of some name or phrase, usually the first letter of each word as is common with acronyms.  The difference between an acronym and initialism is that the abbreviation formed with initialisms is not pronounced as a word, rather you say the individual letters, such as FBI (Federal Bureau of Investigation), CIA (Central Intelligence Agency), and DVD (Digital Video Disk*).

And, of course, if it’s just a shortened form of a word, like “ex.” for “example”, then it’s neither an acronym nor an initialism, rather just an abbreviation.

Another thing about acronyms and initialisms that often causes confusion is whether or not one should place periods after each letter in order to be grammatically correct. Some grammar guides do advise doing so, but just as many say you should not, usually arguing that to add the periods can sometimes make things look messier and it’s already clear by the all-capitals that it’s an abbreviation, so the periods are pointless *snicker*. So really, it’s whatever you prefer as to whether to put periods after the letters of acronyms and initialisms or not.  The important thing is just to be consistent throughout your writing.

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*DVD probably originally stood for “Digital Video Disk”, but today often is changed to stand for “Digital Versatile Disk”

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  • Very interesting. The UK Office for National Statistics (ONS) is very rampant with their acronyms (and initialisms) which they don’t differentiate .One of their favourites (when identifying them) is TLA. Which, as you correctly point out is an “intialism”, and stands for “Three Letter Acronyms”.

  • That’s ridiculous, it’s not a matter of choice, of course you put the period at the end because it’s correct grammar. The period states that the letter preceding is part of a word. Just because you think it looks messy is no excuse to show poor grammar. Ideas like that is what causes laziness in all areas of grammar.

    • Daven Hiskey

      @heshwahn: Everything in grammar is a matter of choice. Once the vast majority of people choose the same thing on some aspect of grammar, that eventually becomes the correct grammatical way to do something. In the end, my philosophy on grammar is summed up better than I could have ever said it by Stephen Fry here.

    • Actually there is a rule regarding periods: they only come if the abbreviation ends up having a different final letter to the full word, e.g. “page” = “pg.” but “Dr” shouldn’t be “Dr.” because “Doctor” also ends in ‘r’. Surprisingly, “Number” = “No”, not “No.”, which is because it’s a contraction of “Numero”.

      • How does the whole pounds = lbs thing work then? hahhaha

        • Lb is an abbreviation of the Latin word libra. The primary meaning of libra was balance or scales (as in the astrological sign), but it also stood for the ancient Roman unit of measure libra pondo, meaning “a pound by weight.

    • @ heshwahn
      Before correcting someone else and calling them lazy, you should correct yourself first. You wrote “Ideas like that is what causes laziness in all areas of grammar.” Ideas “are” and an idea “is”. Ideas “is”. Some may suggest overlooking this is also a lazy way to write. This comment is not intended to be rude or say that I’m always correct. I’m sure I write incorrectly often without realizing it. I probably screwed up somewhere in this comment but I’m not criticizing you or anyone else.

      • In just the first sentence heshwan also connected three independent clauses using only commas, while leaving out the comma for the dependent clause. Now who can find the grammar error in my comment?

  • I was always told not to include the alternative “or” when using the word “whether”. It’s done in this article at the end… Is that not improper? Also, funny pun.

  • The initalism DVD doesn’t stand for Digital Video Disk. It stands for “Digital Versatile Disc”.

    • Correct JP.

      And to the author, DVD has always stood in place for Digital Versatile Disc. It did not “probably originally” stand for Digital Video Disc, and was never changed. You growing up and hearing “Video” instead of “Versatile” is simply over-exposure to the common misinformed consumer. This happens often in society. Another example being N.A.S.A. with common misinformed consumers saying “Aviation” instead of “Aeronautics” for the leading A.

      • Actually Toshiba originally used “Digital Video Disk” until computer corporations complained that it left out their applications, so Toshiba changed the initialism to “Digital Versatile Disk”. Look it up Mr. “Misinformed Consumer”.

        • First off he said, “MAY” have been used. Also, although we are all impressed with your knowledge of DVD, I really didn’t come here to discuss the correct history of that particular term. Mr. “lets get off topic because i have nothing better to say”.

          • Speak for yourself, Joe.~ One way or another people all in all know that it is the same initialism, different words of course, and that it’s the same thing referenced.

    • that’s wat he said sonny jim

  • I actually have a question. We have a team we talk to at my job. The team’s name is “Southwest Ohio Technical Operations Center”. The portion of this name that I argue is an initialism is “SWO.” The “TOC” portion sounds like “tock” so I have no issue pronouncing it as such and recognizing it as an acronym. I just have an issue when the “SWO” is pronounced as an acronym rather than the initialism, which I believe it is. What is the consensus? Is “SWO” an acronym or an initialism?

    • Enigma - Barbara Booface

      Acronyms and Initialisms are taken at face value and encompass all starting letters in their entirety. So, there would be no dividing the SWO from the TOC. Thereby eliminating the need for u to question if it is an acronym or an initialusm. It is either SWOTOC (emphasis on Southwest) or SOTOC. Both versions are pronounceable a d therefore constitutes them as Acronyms. No Initialisms here.

  • What would NRG be? Is it an acronym because it sounds like a word or initialism because you have to pronounce each letter? Is there a more specific term for something like this?

    • Maybe it’s a function of pronunciation?

      I would say each letter in NRG an “Enn Arr Gee”, which is different from the pronunciation of Energy as “”Enn Err Gee”.

  • Along with anon, I have a question about the times where both meanings seem to be applicable.
    Todays tv technology is all about flat screen tv sets. The major types are LCD’s and LCD/LED’s. Recently a new awesome technology has come onboard called OLED. This technology has raised itself to the top of the current chain by winning many “best-of” tv awards. Lcd acronyms out to Liquid crystal display: El-see-dee when spoken. Led acronyms out to Light emitting diode:El-ee-dee when spoken. Oled acronyms out to Organic light emmiting diode but Oh-led when spoken.Why not O.L.E.D? If there are el-see-dees and el-ee-dees why do so many folks seem to say ohled when talking about oled’s? Does this mean that its a matter of if the resulting acronym is easy to pronunce? Elsehduh (LCD) is really hard to say. But LED’s are rarely said to be leeeds or leds. I kinda think I know what to do, now that I have it all written down. But please share your insight.


  • The English language seems to have two big linguistic problems: one with prefixation, another with abbreviation. While I already think prefixation is a lost cause at this point (so humongous is the current mess…), it seems abbreviation isn’t yet, despite many still being curiously confused about it, and existing an important confusion (and therefore mistakes).
    In Spanish, both matters are very clearly regulated nowadays, mostly thanks to the Real Academia Española (or the whole, international Asociación de Academias de la Lengua Española). The periods in the initialisms are optional, but it’s recommended not to write them because they’re not necessary as there are many initialisms written without them, and there’s no real problem, usually.
    Congratulations for your post. We definitely need more like this one. I would add, however, that if one chooses to write the periods on the initialisms, one must notice that the last letter must have a period as well (“N.A.S.A.”, not *“N.A.S.A”)! I’ve seen the last one missing way too many times already… People just don’t usually care. Another thing, abbreviations like “a. m.” must have every element separated by a blank space, since each one is an independent entity, and abbreviations aren’t initialisms (unless one chosses, in cases like this, to treat “a. m.” like one of them, and write “AM” instead). Also, abbreviations are read developing all the elements, while initialisms are simply spelled.
    Keep the good work.
    Best regards,
    Sergi Medina

  • Its always been digital versatile disc.
    Its original use was a superior data storage medium than CD

    • From the Oxford Dictionary:
      “In 1995, rival manufacturers of the product initially named digital video disc agreed that, in order to emphasize the flexibility of the format for multimedia applications, the preferred abbreviation DVD would be understood to denote digital versatile disc.”

  • On Long Island, the prestigious Sag Harbor Institute of Technology for some reason never identifies itself in acronym form.


  • This explanation is on the cusp of being too wordy and lacks clarity and flow as a result.

  • Can an acronym be used to describe when you take, say, the first letter in a series of sentences to form one word? Like:

    What kind of example should I use?
    Oh I know, why not spell out “WORD” with the first letter of each line?
    Really though, it’s getting hard to think of content for the example.
    Damn, last sentence; either way, let me know?

  • Thanks for telling me exactly what I wanted to know, and concisely. Unless I misunderstood your period joke, however, I hope you’ve gotten laid since posting this.

  • Dhananjay Goyal

    Is LOL an initialism or acronym?

    • Enigma - Barbara Booface

      I would definitely say that LOL is an initialism. I am yet to hear of anyone trying to pronounce it in reference as a whole word pronounced as “lol” and that is what is needed for it to be an acronym. From inception, it has always been referred to as the spoken letters L-O-L, which, in turn, makes it an Initialism.

  • Language pronunciation always evolves to the convienience of a given majority. Otherwise, Spanish and French would still be Latin and et cetera.
    I have five pair of Nike’s to go walking in. Why would I want to wait eight weeks for a wagon train, going each way, fighting off undesirables, for a pair of boots that cost ninety- six cents, as Laura Ingalls had to do? I coo jez keel me a rabinin meek me apara moccasins, buh thad be polilcul eencoorec these dais…

    yukyuk…(i.e. LOL or l.o.l. or LMFAO)

  • I’ve never heard anyone say L-O-L, perhaps excepting my parents. I now most often see “lol” (not “LOL”), as with other acronyms (such as “radar” or “laser”) which have graduated to the wider English lexicon.

    However, YMMV lol (IMO)

  • Yet another source claims “ATM is an acronym for ‘automated teller machine’.” Are you saying “ATM” is pronounced “a-tim”?

  • Digital versatile disc not digital video disc.

  • Surprised that no one commented on “ex.” as an abbreviation for “example” (or more likely, “for example”). This is becoming more common, and may be considered acceptable already in some areas, but I think this abbreviation has only arisen as people have forgotten the original “e.g.” [ex gratia] as meaning “for example.”

  • The article uses DVD as an example of an Initialism and then erroneously suggests that it stands for Digital Video Disk. This is a common error, the correct term is Digital Versatile Disk