acronym

> acronym
A word that, like some ABBREVIATIONS, is formed from the initial letters of several words. Unlike abbreviations, however, acronyms are pronounced as words rather than as just a series of letters. For example, OPEC (Organization of Petroleum Producing Countries) is pronounced o-pek and is thus an acronym, unlike USA (United States of America) which is pronounced as a series of letters and not as a word (oo-sa or yoo-sa) and is thus an abbreviation.
Acronyms are written without full stops, as in UNESCO (United Nations Educational, Scientific and Cultural Organization). Mostly acronyms are written in capital letters, as in NASA (National Aeronautics and Space Administration). However, very common acronyms, such as Aids (Acquired Immune Deficiency Syndrome), are written with just an initial capital, the rest of the letters being lower case.
Acronyms that refer to a piece of scientific or technical equipment are written like ordinary words in lower-case letters, as laser (light amplification by simulated emission of radiation.