An acronym is a word formed from the first letters of a series of words, such as:
* NATO (North Atlantic Treaty Organization)
* NASA (National Aeronautics and Space Administration)
* LASER (Light Amplification by Stimulated Emission of Radiation)
Initialism is a related term, but it refers to a word formed from initials that are pronounced separately, such as:
* FBI (Federal Bureau of Investigation)
* USA (United States of America)
* BBC (British Broadcasting Corporation)
So, while "radar" and "scuba" are both formed from initials, they are considered acronyms because they are pronounced as a single word.