RAS syndrome

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. Three common examples are "PIN number"/"VIN number" (the "N" in PIN and VIN stands for "number") and "ATM machine" (the "M" in ATM stands for "machine"). The term RAS syndrome was coined in 2001 in a light-hearted column in New Scientist.

Many style guides advise against usage of these redundant acronyms in formal contexts, but they are widely used in colloquial speech.