Acronym vs. Initialism — What’s the Difference?

In spoken and written language, we often shorten long words and phrases into different kinds of abbreviations. Sometimes, single words are abbreviated, like when we say “prep” for prepare or when we write “min” for a minute. 

Phrases with multiple words are often shortened into initialisms and acronyms, which are both abbreviations that use the first letter of each word. Acronyms and initialisms are easier to remember and to pronounce than the full phrases they replace. Below, we’ll discuss the difference between these two types of abbreviations.

Acronym vs. Initialism Key Takeaways

Although acronyms and initialisms are both formed the same way, they have one key difference: how we say them.

All the letters in an acronym or initialism are capitalized — or at least they start out that way, as we shall see below.

Acronym — An abbreviation of a phrase that takes the first letter of each word, and is pronounced as its own word.

  • Examples: PIN (personal identification number), NASA (National Aeronautics and Space Administration)

Initialism — An abbreviation of a phrase that takes the first letter of each word, and is pronounced letter by letter.

  • Examples: USA (United States of America), FBI (Federal Bureau of Investigation)

Examples of Acronyms

These are acronyms, so they are all pronounced as words. 

  • NASA — National Aeronautics and Space Administration
  • NATO — North Atlantic Treaty Organization
  • SONAR — Sound Navigation and Ranging
  • POTUS — President of the United States
  • SWAT — Special Weapons and Tactics

Examples of Initialisms

These are initialisms, so each letter is pronounced. 

  • DIY — Do It Yourself
  • FAQ — Frequently Asked Questions
  • GPS — Global Positioning System
  • NBA — National Basketball Association
  • UFO — Unidentified Flying Object
  • ASAP — As Soon As Possible (Sometimes pronounced “ay-sap,” like an acronym.)

Acronyms Can Become Regular Words

The Oxford Style Guide points out that some words begin as acronyms but are used so frequently and generally that they become treated as regular words, spelled with lowercase letters. 

As an example, they point out that LASER, which initially stood for Light Amplification by Stimulated Emission of Radiation, has become the common, lower case word “laser” that we know and use today. Scuba, which technically stands for Self-Contained Underwater Breathing Apparatus, has also become so common that it is often spelled in lowercase.

Acronyms and Initialisms as Memory Tools

Acronyms and initialisms can be used as memory tools, also called mnemonic devices.

For example, the acronym HOMES is used to remember the Great Lakes in North America: Huron, Ontario, Michigan, Erie, and Superior.

Initialisms can be turned into acrostics, where a phrase or poem is used to help remember the first letter. For example, in biology class, students are tasked with memorizing the levels of taxonomy: Kingdom, Phylum, Class, Order, Family, Genus, and Species. 

That can be hard to remember! But if you learn the phrase “King Phil Came Over For Great Soup,” you’ve learned the first letter — in order — of each of the taxonomic levels.

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