PIN number.

A lot of people say that PIN number is a redundancy because PIN is an acronym for ''personal identification number'' and adding ''number'' at the end is redundant. But I don't think that it's really that redundant. If someone said just ''PIN'' someone could think they were talking a pin that you pin things with. Saying ''PIN number'' is useful to avoid confusion with a safety pin or whatever kind of pin.

If someone were talking about their PIN number and they just said ''PIN'' someone could think they were talking about a pin and not their PIN number.

PIN number is not a redundancy but a useful term to avoid confusion with a pin.

I suppose it is a redundancy, but I don't suppose it's any worse than a double negative. As has been stated here many times in the past when the topic turned to double negatives, language isn't logical; it's about communication. If PIN number gets the idea across clearer than just "PIN" (there are several types of pins...hair pins, bowling pins, etc.), then who really cares if it's technically a redundancy?

Language pedants would likely argue that it's a tautology. But it's entirely natural to say "PIN number" in spoken English. Arguably, one might claim that it is rather redundant in the written language which tends to be more deliberate and less extemperaneous than speech.

Not a "big deal" though.

It is redundant, but far from unique. After all, most people enter their PIN numbers at an ATM machine.

PIN numbaaaaaaaaaa!