Why is it π? Pi is just a number. We write the names of most numbers with ordinary digits like the number twenty eight is written 28. The name of the number that is half of eleven is 5½ or 5.5. So why isn't pi written like this too?

If you try to write the true name of pi this way it turns out to be a terrible name. I had an uncle named Leroy Frances and a grandfather, Oscar Cornelius. They both had nick names. You can probably see why. Since pi is an irrational number... (ok, just a minute) Pi is defined as the ratio of the circumference of a circle to its diameter. This is interesting. Pi is an irrational ratio? (oh well, we'll leave you to research that oxymoron with some of the links below. Back to what I was saying.) Since pi is an irrational number, its name written in digits has no end. It goes forever without ever repeating. Now that is a bad name. Since pi is a popular number used in many calculations it was given a nick name.

Wouldn't you rather write π than 3.14159 26535 89793 23846 26433 83279 50288 41971 69399 37510 58209 74944 59230 78164 06286 20899 86280 34825 34211 70679... (just getting started). In the links below you can find pi to 1,000,000 decimal places.

Some people just write 3.14 for pi, but this may not be accurate enough for some calculations. We'd hate it if a bridge would collapse, a building would fall down or a plane would crash just because someone did not use an accurate enough number in their calculations. The more correct digits of pi that are used in a calculation, the more accurate the answer. So be careful. 3.14 might not always be accurate enough, but it sure makes it nice to celebrate on March 14.