Acronym
An acronym is an abbreviation consisting of initial letters that are read like an ordinary word.
Examples
English radar (pronounced [ˈreɪdɑɹ] ), from radio detection and ranging.
Comments
Acronyms contrast with alphabetisms, which are pronounced with the names of the letters (e.g. CD, HTML).
Polysemy
Sometimes acronym is used for abbreviations more generally, i.e. also for alphabetisms.
Origin
From Greek akro- 'tip' and -oonym- 'name'. The first attestation in the OED is from 1943.
