How long is a piece of string?

Well, I have a piece of string and it’s about 9.5cm long.  I could give you the answer in inches, or take it to some laboratory where lasers will be used to measure it to the nearest nanometer.  Or maybe you’re asking a totally different question, like how long will it last before it rots away into nothing.

In any case, I think the answer is that it depends how you want to measure it.