RAS syndrome (short for "redundant acronym syndrome syndrome"), also known as PNS syndrome ("PIN number syndrome syndrome", which expands to "personal identification number number syndrome syndrome") or RAP phrases ("redundant acronym phrase phrases"), refers to the use of one or more of the words that make up an acronym or initialism in conjunction with the abbreviated form, thus in effect repeating one or more words.
A person is humorously said to suffer from RAS syndrome when he or she redundantly uses one or more of the words that make up an acronym or initialism with the abbreviation itself. Usage commentators consider such redundant acronyms poor style and an error to be avoided in writing, though they are common in speech. The degree to which there is a need to avoid pleonasms such as redundant acronyms depends on one's balance point of prescriptivism (ideas about how language should be used) versus descriptivism (the realities of how natural language is used). For writing intended to persuade, impress, or avoid criticism, usage guides advise writers to avoid pleonasm as much as possible, not because such usage is always "wrong", but rather because most of one's audience may believe that it is always wrong.
The similar term PNS syndrome (which expands to "PIN number syndrome syndrome", and further to "personal identification number number syndrome syndrome") was coined by Usenet users before the coining of RAS Syndrome.
- ATM machine (automated teller machine machine)
- LCD display (liquid crystal display display)
- PIN number (personal identification number number)
Reasons for use 
There are several linguistic explanations for the prevalence of RAS syndrome:
- A limited amount of redundancy can improve (or seem to the speaker to improve) the effectiveness of communication. The pure-logic ideal of zero redundancy is seldom maintained in natural languages, because they have evolved some kinds of redundancy checks. A phonetic example of that principle is the need for spelling alphabets in radiotelephony. Some instances of RAS syndrome can be viewed as syntactic examples of the principle. The speaker wishes to gently reinforce the meaning of an acronym or initialism, especially in pedagogical contexts (whether formal or informal). In such cases, the redundancy may help the listener by providing context and decreasing the 'alphabet-soup' quality of the communication.
- Acronyms and initialisms from foreign languages are often treated as unanalyzed morphemes when they are not translated. For example, in French, "le protocole IP" (the Internet protocol protocol) is often used, while in English "please RSVP" (roughly "please respond please") provides an example of a redundant French initialism.
- The principle of not analyzing also applies within one language. For example, people who work regularly with the term AC (alternating current) experience some degree of treating the word both in sound (//) and in appearance as an unanalyzed lexeme. They do not forget what its expanded form is, but neither do their brains shift to the expanded form without a cue. Thus the redundancy in phrases such as "ATM machine" can be likened to that in the phrase "red in color". It is a degree of redundancy born of treating objects (in the abstract philosophical or computing senses of that word) as black boxes to be strung together, which is a natural aspect of human cognition.
Sometimes the presence of repeated words does not create a redundant phrase. For example, a "redundant RAID (redundant array of inexpensive/independent disks)" may in fact be a backup RAID in the system being described; "laser (light amplification by stimulated emission of radiation) light" is light produced by a light amplification process.
See also 
- Garner, Bryan A. (2000) The Oxford Dictionary of American Usage and Style. Oxford and New York: Oxford University Press.
- Clothier, Gary (8 November 2006). "Ask Mr. Know-It-All". The York Dispatch.
- Newman, Stanley (December 20, 2008). "Sushi by any other name". Windsor Star. p. G4.
- "Feedback" (fee required). New Scientist (2285). 2001-04-07. p. 108. Retrieved 2006-12-08.
- RAS syndrome newsgroup on Usenet (alternative free web access using Google Groups)
- "uk.games.video.dreamcast - uk.net.news.config | Google Groups". Groups.google.com. 1999-08-20. Retrieved 2009-05-22.
- "Redundant Acronym Phrases".
- Singh, S.K. Bank Regulations. Delhi: Discovery Publishing House. ISBN 81-8356-447-X.
- Brians, Paul. "LCD display". Common Errors in English Usage. Retrieved 05-01-2012.
- "Sick of acronyms?". Electronics Weekly. 25 April 2001.
- "LINGUIST List 4.532: Last Posting: Acronyms". Linguistlist.org. Retrieved 2009-05-22.