RAS syndrome, where RAS stands for redundant acronym syndrome (making the phrase "RAS syndrome" autological) is the redundant use of one or more of the words that make up an acronym in conjunction with the abbreviated form. This means, in effect, repeating one or more words from the acronym. For example: PIN number (expanding to personal identification number number) and ATM machine (expanding to automated teller machine machine).
The term RAS syndrome was coined in 2001 in a light-hearted column in New Scientist.[1][2][3]
A person is said to "suffer" from RAS syndrome when they redundantly use 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 that is best avoided in writing, especially in a formal context, though they are common in speech.[4] 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).[5] For writing intended to persuade, impress, or avoid criticism, many 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.[6]