An acronym is an abbreviation formed using the initial letters of a multi-word name or phrase. Acronyms are often spelled with the initial letter of each word in all caps with no punctuation.
In English, the word is used in two ways. In the narrow sense, an acronym is a sequence of letters (representing the initial letters of words in a phrase) when pronounced together as a single word, like NASA, NATO, or laser. In the broad sense, the term includes this kind of sequence when pronounced letter by letter (such as GDP or USA). Sources that differentiate the two often call the former acronyms and the latter initialisms or alphabetisms. However, acronym is popularly used to refer to either concept, and both senses of the term are attributed as far back as the 1940s. Dictionary and style-guide editors dispute whether the term acronym can be legitimately applied to abbreviations which are not pronounced as words, and there is no general agreement on standard acronym spacing, casing, and punctuation.
The phrase that the acronym stands for is called its expansion. The meaning of an acronym includes both its expansion and the meaning of its expansion.
