It seems that 98.2% of the general population really has no idea what an acronym is, or how they differ, if at all, from abbreviations. 99.4% of the general population has no idea what an initialism is. So, to clear up any confusion and prevent further embarrassment when talking with friends, speaking in public, or having discussions in meetings, this page explains what abbreviations, acronyms, and initialisms are and provides examples of each. After reading this, there is no excuse for using the wrong term.

(ə-brēˌvē-āˈshən) - a shortened or contracted form of a word or phrase, used to represent the whole
Examples:

• Dr. - Doctor (dokˈtər)
• BTW - By The Way
• lb - Pound, as in a unit of weight (Meghan Jones provides an explanation for this, here.)
• Mr. - Mister (mĭsˈtər) - Used as a courtesy title before the surname, full name, or professional title of a man.
• Mrs. - Missus (ˈmisiz) - Mrs. is the diminutive form of Mistress. It came from the word “mistress” the feminine form of “mister.”
• U.S. - for United States

Bonus Material: There is a special HTML tag for abbreviations. It is <abbr></abbr>, and it should include a title attribute which spells-out the abbreviation. And since initialisms and acronyms are just special cases of abbreviations, this tag should be used for those as well.

Here is an example:

<abbr title=“National Aeronautics and Space Administration”>NASA</abbr>

(ăkˈrə-nĭm) - an abbreviation that is pronounced as a word
- Similar, see Backronym, below.
Examples:

• ArcGIS - This is actually a combination of an acronym (ARC) and an initialism (GIS), seldom (i.e. never) referred to as an acronysm and even more seldom written acronism (ăkˈrə-nĭzˌəm), and should not to be confused with an anachronism (ə-năkˈrə-nĭzˌəm) which is something different altogether. ArcGIS stands for Aeronautical Reconnaissance Coverage Geographic Information System. Very few people know this, and even fewer care. Now, however, ArcGIS simply refers to the suite of software products produced by ESRI (defined below).
• ARIA - Accessible Rich Internet Applications
• ASAP - As Soon As Possible - sometimes used as an initialism
• ASCII - American Standard Code for Information Interchange - a character encoding standard for electronic communication
• BOHICA - Bend Over Here It Comes Again - The name given by employees to many of the programs implemented by INL.
• CAPTCHA - Completely Automated Public Turing test to tell Computers and Humans Apart - The acronym (pronounced KAP-chə) is the challenge-response test just about everyone has seen when trying to access their online accounts. Here's a recent example. captcha.jpg
• Cron - As in Cronjob. Command Run On Notice
• DOS - Disk Operating System - What we had before Windows. (Yes, I know that's a pretty lame explanation, but good enough.)
• ESRI - Environmental Systems Research Institute - The acronym (pronounced 'ez-ree') is now the preferred usage however, it is still spoken as an initialism, particularly by long-time (i.e. old) ESRI software users.
• FOMO - Fear Of Missing Out - The sense that when you're presented with new information, whether via email, seeing a new article in your Facebook or Twitter feeds, or scrolling through notifications on your phone, that if you don't stop everything and consume it immediately, you're going to miss out on something super important that everybody else in the world knows about but you.
• F _ _ _ - Fornication Under Consent of the King - The most popular acronym in the world, and one that few even knew was an acronym.
• JSON - (pronounced “jason” according to its inventor, Douglas Crockford), stands for JavaScript Object Notation
• Laser - Light Amplification of Stimulated Emission of Radiation - Everyone knows what a laser is.
• LiDAR - Light Detection and Ranging - A laser version of Radar. (See Radar, below.)
• LORAN - Long Range Navigation - A long range system developed in the United States during World War II.
• NASA - National Aeronautics and Space Administration
• NATO - North Atlantic Treaty Organization
• OPEC - Organization of the Petroleum Exporting Countries
• PARC - Palo Alto Research Center - PARC is where the computer mouse came from. They did a few other things as well.
• PIN - Personal Identification Number, used for just about everything in the world.
• Radar - RAdio Detecting And Ranging
• Scuba - Self-Contained Underwater Breathing Apparatus
• SMART - As used in 'Smart Goals.' Stands for Specific, Measurable, Attainable, Relevant, Time-based. That's all we really know about this having never been able to successfully set a Smart Goal.
• Sonar - SOund Navigation And Ranging
• SQL - Stands for Structured Query Language. Even though many people pronounce this as a word (sequel), and thereby making it an acronym, that's wrong. It's really an initialism (see below in the Initialism section) and it should be pronounced that way. (BTW, SEQUEL, was a real acronym back in the 70s when it stood for Structured English Query Language, but was dropped because it was a trademark of an airplane company.) BTW, this is the only three-letter acronym that I have at the moment, but like I mentioned, it's really used incorrectly.
• SWOT - Strengths, Weaknesses, Opportunities, and Threats - Used as a structured planning method to evaluate these key areas of an organization. My experience has shown that this is just another thing that some people like to do and then try to pass it off as actually being useful.
• WYSIWYG - Pronounced (WIZ-ee-wig) - Stands for “What You See Is What You Get.” That phrase, “what you see is what you get”, was originally created by Flip Wilson's character Geraldine and it inspired researchers at PARC (and elsewhere) to use the acronym for computer software that allows content to be edited in a form that looks like it will when printed. Pretty much a useless acronym now, but was popular at one time.
• YAGNI - Stands for “You Aren't Gonna Need It” - a principle of extreme programming (XP) that states a programmer should not add functionality until deemed necessary.

(ĭ-nĭshˈə-lĭzˌəm) - an abbreviation that is pronounced one letter at a time
Examples:

• A11Y - Accessibility, the letter “a,” followed by 11 letters, followed by “y”
• aka - also known as
• API - Application Programming Interface
• ASAP - As Soon As Possible - sometimes used as an acronym
• BFF - Best Friends Forever
• CD - Compact Disc
• CGI - Common Gateway Interface - an interface specification that enables web servers to execute an external program to process HTTP/S user requests. These programs are commonly referred to as CGI scripts. Examples include CGI scripts that process form submissions.
• CIDR - Classless Inter-Domain Routing (I use this all the time.)
• CSS - Cascading Style Sheets
• DVD - Digital Video Disc
• DYK - Did You Know
• DYC - Do You Care
• e.g. - from the Latin exemplī grātiā ‎(“for example”)
• EPA - Environmental Protection Agency
• FAQ - Frequently Asked Questions
• FBI - Federal Bureau of Investigation
• fka - formerly known as
• FOUC - Flash Of Unstyled Content (also flash of unstyled text or FOUT) - the condition where a web page appears briefly with the browser's default styles prior to loading an external stylesheet, due to the web browser engine rendering the page before all information is retrieved. Related problems include flash of invisible text (FOIT) and flash of faux text (FOFT).
• FTP - File Transfer Protocol
• FYI - For Your Information
• G11N - Globalization, the letter “g,” followed by 11 letters, followed by “n”
• GIS - Geographic Information Systems
• GPS - Global Positioning System
• HTML - HyperText Markup Language
• I18N - Internationalization, the letter “i,” followed by 18 letters, followed by “n”
• IBM - International Business Machines (also, I've Been Moved, as reported by IBM employees at one time)
• ICYMI - In Case You Missed It
• IE - Internet Explorer. Many people confuse IE with a web browser. Technically, IE is was (it officially died on June 21, 2022) a Microsoft Internet document viewer. A true web browser will open and display web-based files that conform to the W3C standards. IE opens opened and displays displayed web-based files that conform conformed to Microsoft's standards.
• i.e. - from the Latin id est (‎“that is”)
• L10N - Localization, the letter “l,” followed by 10 letters, followed by “n”
• nka - now known as
• P13N - Personalization, the letter “p,” followed by 13 letters, followed by “n”
• PhD - Stands for “Doctor of Philosophy” which appears to be a misnomer since most have never taken a philosophy course in their lives.
• PHP - PHP is a very powerful scripting language. In the beginning (1995) “PHP” stood for “Personal Home Page.” But that's changed. It's now a recursive abbreviation and stands for “PHP - Hypertext Preprocessor.”
• PII - Personally Identifiable Information. Examples include: Full name/usernames, Home address/mailing address, Email address, Credit card numbers, Date of birth, and Phone numbers.
• QR (as in QR code) - Quick Response
• SFTP - SSH FTP (File Transfer Protocol), essentially Secure FTP
• SQL - Stands for Structured Query Language and although most people pronounce this as a word, and therefore consider it an acronym, that's wrong. It's really an initialism and it should be pronounced that way. See also SQL in the Acronym section, above.
• SSH - Secure Shell
• TFS - Team Foundation Server - something from Microsoft supposedly to aid in the development of software. Here's an interesting and little known fact. It was originally called “Productivity Optimization Server,” however, confusion resulted since the phrase “Microsoft POS” referred to multiple Microsoft products.
• TL;DR - short for “Too Long; Didn't Read” - Internet slang to say that some text being replied to has been ignored because of its length. Variations include: ToS;DR - “Terms of Service; Didn't Read”and DC;DR - “Don't Care; Didn't Read”,
• TMI - Too Much Information, or Three Mile Island, depending on the context.
• URL - Uniform Resource Locator and is a reference to a resource on the Internet. It's usually just referred to as the web address. Some people will pronounce this as if it was an acronym (earl) but that's wrong, and just sounds stupid.
• UX - Guess this is an initialism with a typo. It stands for User Experience.
• VCS - Version Control System, a system responsible for managing changes to software, e.g. GIT or SVN
• VHS - Video Home System (nobody ever knew this!)
• XKCD - Ok, this is NOT an initialism. According to this, it's “just a word with no phonetic pronunciation.” I'm putting it here, anyway, because this is probably where someone will go to look for it. XKCD (or xkcd) is “A webcomic of romance, sarcasm, math, and language.”

Notes on Initialisms
Many people would simply call these abbreviations, which is fine.
Many more people would call these acronyms, which is not fine.

(ŭᴛʜ′ər) - not an abbreviation, and it's not a word, but it's pronounced as if it was a word.
Examples:

• BLOG - You can pronounce this as a word, but it's not an abbreviation, either. It's a truncation of “web log.” A blog is essentially a website where the owner publishes content to the web. They became popular because they don't require any technical skills. Blogs often allow readers to comment, which are also then published on the site.
• email - Concatenation of “electronic” and“mail.” Used to be that it was written e-mail but I guess Websters decided to change that.
• QWERTY - Pronounced as a word but it's not an abbreviation for anything, it just refers to the standard keyboard layout that’s been in use since people knew what a “carriage return” was.
• VLOG - Can't easily pronounce this, but it's shorthand for “video log.” Basically a blog but the medium is video.

(băkˈrə-nĭm) - a constructed phrase that purports to be the source of an acronym.
Examples:

• MOAB - Mother of All Bombs (in response to Saddam Hussein's “mother of all battles,” but really stands for Massive Ordnance Air Blast bomb)
• SPAM - Something Posing As Meat