“Get that up on that mistakes blog of yours this second!” retorted a friend when I used the expression ‘PIN number’ in an email in passing.
It took me a few moments to work it out.
A PIN is, of course, a Personal Identification Number, and so is a ‘number’ by definition. You don’t need the extra ‘number’.
Likewise, and of particular interest and relevance to writers, are ISSN and ISBN – don’t tag a ‘number’ to those either, as they are International Standard Serial Number and International Standard Book Number, respectively.
PDF format, ADSL line, DVD disc and ATM machine – also tautologies, one and all, and you’re bright enough to work out why.
Wonderfully, this mistake even has a name, which comes with its own built-in irony – RAS Syndrome. That’s Redundant Acronym Syndrome Syndrome.
RAS Syndrome is very common in speech, of course, and nothing much to worry about in writing (unless you have a pedantic pal): it won’t cost you anything, an editor may not even notice it, and a sub-editor will cut the superfluous word if you do insert it in finished copy. Still, always nice to get it right, though.
Who’s got some others?