The denotational definition of an "acronym
" requires the acronym to be pronounceable as a word.

Here are some examples true acronyms.

• NASA = National Aeronautics and Space Administration
• NATO = North Atlantic Treaty Organization
• BIBLE = Basic Instructions Before Leaving Earth (note: some acronyms such as this one may many alternative words)

Notice how connecting words such as "and" may or may not be part of the acronym.

The word LASER (Light Amplification by the Stimulated Emission of Radiation) is an acronym, often written as "laser".
The connecting words here are "by", "the" and "of".

Another acronym is RADAR = RAdio Detection and Ranging, where the first two letters of "RAdio" are used to create the acronym.

The German acronym FLAK = Fliegerabwehrkanone (also "Flugabwehrkanone") comes from the German words "Flieger" (flying), "Abwehr", (defense) and "Kanone" (canon).

So, FBI = Federal Bureau of Investigation is not an acronym since no pronounceable word is formed by the letters. Instead, it is an "initialism".

In general usage, such letters are often called acronyms, with the letters pronounced individually.

Sometimes, an acronym may be given other definitions, often in jest, satire, etc.

• NSA = National Security Agency (the official definition)
• NSA = No Such Agency
• NSA = Never Say Anything

Some acronyms are defined in terms of other acronyms. What, for example, is SAX?

The acronym

• SAX = Simplified API for XML

defined using the following.

• API = Application Program Interface
• XML = Extensible Markup Language

A TLA describes itself my the defined meaning of the acronym.

• TLA = Three Letter Acronym

A TLA is a TLA.

Here are some types of computer memory.

• ROM = Read Only Memory
• RAM = Random Access Memory

ROM is a TLA, and RAM is a TLA.

The acronym GNU (GNU is Not Unix) refers to itself recursively (in a circular and thereby never ending way).

A recursive acronym uses itself in the letter definitions.

The pattern of creating acronyms is human and is an example of the principle of least effort.

Linguist George Zipf studied word frequency usage and found that across many different languages, people will (among other things) introduce newly created shorter words to avoid longer harder-to-pronounce words. Some examples include the following.

• nicknames
• acronyms
• telegraph abbreviations
• text messaging

This principle is often called the "Principle of least effort".

In more precise terms, the frequency of usage of any word is inversely proportional to the rank of that word in the frequency tables of words (in the language being used). In a general way, few words are used often while most are used much less often. This principle is similar to the Pareto principle (to be added later).

Acronyms have been used since antiquity.