In typography, a set of of letters which form a pronounceable word, each letter also standing for another word, such as NASA, which stands for National Aeronautic and Space Administration, or TIFF, which stands for Tagged Image File Format. Stylistically, an acronym is typeset in all capital letters, usually without periods between the letters.
Often, an acronym will enter the lexicon of a language as a word in its own right, and after a while it may not even be obvious that it is an acronym. For example, the word laser began life as an acronym for light amplification by stimulated emission of radiation.