Informal situations can include chats, texts and e-mails between friends or close family. In these cases, acronyms may be used however the speakers desire. Common courtesy, though, dictates that each person should at least be somewhat familiar with the acronyms in play. Acronyms that have appeared in online chat and progressed into daily language include LOL (laughing out loud), AIR (as I recall/remember), ASAP (as soon as possible) and SIG (special interest group).
When sending correspondence to a more formal person such as a teacher, colleague or boss, it is sometimes acceptable, though generally unwise, to use informal acronyms. For schoolwork and most pieces intended for publication, the writer should never use informal acronyms. In formal situations such as these, commonly recognized acronyms that refer to organization names or titles may be used if they help avoid repetition. For formal writing situations, teachers and editors advise authors to write out the full name or title the first time it is used, follow it with the acronym in parenthesis and then use the acronym throughout the rest of the piece.
Exceptions to the “write it out the first time” rule are acronyms that are so well-known by their abbreviations that most people do not know or remember what they stand for. Scuba (Self-Contained Underwater Breathing Apparatus), sonar (SOund Navigation And Ranging), and radar (RAdio Detection And Ranging) are examples of well-known acronyms. These acronyms also do not require capitalization unless they belong to a formal name or are the first word in a sentence.
Closely related to the acronym is the initialism, another kind of abbreviation in which each letter stands for something, but the whole is pronounced by its letters rather than as a word. Examples of initialisms are NFL, MRI and BTW. Linguistic researchers speculate the difference between the acronym and initialism will soon be lost to the masses and everything abbreviated in such a manner will be referred to as an acronym.