What the heck is an initialism? It's a type of abbreviation, but it's different from an acronym.
Today's topic is the difference between abbreviations, acronyms, and initialisms.
Unfortunately, you can't call any abbreviation made up of a phrase's first letters an acronym. Sometimes they are initialisms.
But let's back up. Any shortened form of a word is an abbreviation, for example, "etc." for "etcetera" and "Oct." for "October;" but acronyms are special kinds of abbreviations that can be pronounced as words, such as "NASA" (National Aeronautics and Space Administration) and "OPEC" (Organization of the Petroleum Exporting Countries). This makes acronyms a subset of abbreviations. All acronyms are abbreviations, but not all abbreviations are acronyms.
Initialisms are another type of abbreviation. They're often confused with acronyms because they are made up of letters, so they look similar, but they can't be pronounced as words. "FBI" and "CIA" are examples of initialisms because they're made up of the first letters of "Federal Bureau of Investigation" and "Central Intelligence Agency," respectively, but they aren't usually pronounced as words. Insiders sometimes call the FBI "fibby" and the CIA "see-uh," but most of the world says "F-B-I" and "C-I-A," so they are initialisms.
Initialisms are made from the first letter (or letters) of a string of words, but can't be pronounced as words themselves. Examples include “FBI,” “CIA,” “FYI” (for your information), and “PR” (public relations).
Acronyms are made from the first letter (or letters) of a string of words but are pronounced as if they were words themselves. Examples include “NASA” and “NIMBY”(not in my backyard).
Abbreviations are any shortened form of a word.
Sometimes acronyms like "scuba" become so common that they're accepted as words in their own right. "Scuba" was originally an acronym for "self-contained underwater breathing apparatus," but now dictionaries include it as a word.