Acronym

An acronym is a word formed from the initial letters or parts of a phrase and typically pronounced as a word.

Abbreviation: A shortened form of a word or phrase. Acronyms are one kind of abbreviation.
Backronym: A phrase devised to fit the letters of an existing word or name. It reverses the usual direction: the word comes first, and the expansion follows.
NASA: The United States agency responsible for civilian space exploration and aeronautics research. Its name is commonly pronounced as a word formed from the agency's initials.
Acronym (initialism distinction): The distinction between pronounceable initial-letter words and abbreviations spoken as letter names. The boundary clarifies why NASA is an acronym while FBI is an initialism.
Initialism: An abbreviation formed from initial letters and pronounced letter by letter. Unlike an acronym, an initialism is usually spoken as separate letter names.
Syllabic abbreviation: An abbreviation formed from syllables or other parts of words, often pronounced as a word. It shows how acronym-like words can combine more than initial letters.
Radar: A system that detects objects using reflected radio waves. Its acronym origin is no longer apparent to many speakers.
Contraction (grammar): A shortened form made by omitting letters or sounds, often marked with an apostrophe. Contractions shorten expressions but do not form words from phrase initials.
Clipping: A word-formation process that shortens a longer word by removing part of it. Acronyms can draw on parts of words, not only their initial letters.
Pronunciation: The conventional way a word or language is spoken. Pronunciation distinguishes word-like acronyms from letter-by-letter initialisms.

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