[ ih-nish-uh-liz-uhm ]


  1. a set of initials representing a name, organization, or the like, with each letter pronounced separately, as FBI for Federal Bureau of Investigation.
  2. the practice of using initials or forming words from initials.

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Grammar Note

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Word History and Origins

Origin of initialism1

First recorded in 1895–1900; initial + -ism


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More About Initialism

What does initialism mean?

An initialism is a term formed by abbreviating a phrase by combining certain letters of words in the phrase (often the first initial of each) into a single term.

Common examples of initialisms include FBI (an initialism of Federal Bureau of Investigation) and TMI (an initialism of too much information).

What’s the difference between an acronym and an initialism?

Initialism is sometimes used as a synonym for acronym, but most technically it refers to an abbreviation in which each initial is pronounced separately, as in FBI and TMI.

Although acronym is sometimes used generally to refer to any term formed from this kind of abbreviation, it typically refers to ones that can be pronounced as a word, like NASA (an acronym for National Aeronautics and Space Administration) and FOMO (a slang acronym for fear of missing out).

Still, most people don’t distinguish between acronyms and initialisms—they usually end up calling most abbreviations acronyms.

Both terms are often associated with their use in certain fields that use a lot of technical terms, like science, tech, and the military. But they’re popular in all kinds of contexts since they’re an easy way to make long phrases much shorter.

Example: MIA is an initialism that stands for “missing in action.”

Where does initialism come from?

The first records of the word initialism come from right around 1900. It comes from a combination of the word initial, from the Latin initium, meaning “beginning,” and the suffix ism, which in this case refers to a usage within a language (as seen in words like colloquialism).

Both initialisms and acronyms are typically formed from the initials of words. For example, some common words started as this type of abbreviation: radar comes from the phrase radio detection and ranging; laser comes from lightwave amplification by stimulated emission of radiation. As you can see in these two terms, such abbreviations are not always formed from just the first initial of each word, and not every word in the phrase always contributes a letter.

In the most technical sense, such terms are acronyms when they can be pronounced as words (like NASA), and they’re initialisms when they are pronounced one letter at a time (like FBI). Common text and chat abbreviations like brb and ttyl are technically initialisms. Still, in all these cases, people are more likely to call them acronyms.

Some abbreviations can be pronounced both as single words and letter-by-letter. For example, ASAP (for as soon as possible) is commonly pronounced A-S-A-P, but it can also be pronounced AY-sap.

Initialisms are commonly used to abbreviate organization names (as in FBI, CIA, NBA, and NFL), but they’re used in all different contexts, including science, the military, government, slang, and pop culture.

Did you know ... ?

What are some synonyms for initialism?

What are some words that share a root or word element with initialism

What are some words that often get used in discussing initialism?


What are some words initialism may be commonly confused with?



How is initialism used in real life?

Initialisms are used in all kinds of contexts, but most people just call them acronyms. Which is really OK.



Try using initialism!

True or False? 

Initialism and acronym always mean the same exact thing.