en.wikipedia.org/wiki/Pi

The number π is a mathematical constant, the ratio of a circle's circumference to
its diameter, commonly approximated as 3.14159. It has been represented by ...

www.mathsisfun.com/numbers/pi.html

all the way around the circle) will be Pi. Pi (the symbol is the Greek letter π) is: ...
In fact π is not equal to the ratio of any two numbers, which makes it an irrational
...

www.livescience.com/29197-what-is-pi.html

Apr 30, 2013 ... Pi represents the ratio of the circumference of a circle to its diameter. Pi is an
irrational number that never ends; the decimals go on forever and ...

www.piday.org/learn-about-pi/

Pi (π) is the ratio of a circle's circumference to its diameter. Pi is a constant
number, meaning that for all circles of any size, Pi will be the same. The diameter
of a ...

www.math.com/tables/constants/pi.htm

Pi is a name given to the ratio of the circumference of a circle to the diameter.
That means, for any circle, you can divide the circumference (the distance around
...

nrich.maths.org/2490

Read all about the number pi and the mathematicians who have tried to find out
its value as ... is the ratio of the circumference of a circle to its diameter.

c2.com/cgi/wiki?ValueOfPi

Seriously, it does make sense to define "pi" as a defined constant - not because
... The text states, "the ratio of the diameter and circumference is as five-fourths to
...

www.angio.net/pi/whypi.html

Pi (π) is the ratio of the circumference of a circle to its diameter. It doesn't matter
how big or small the circle is - the ratio stays the same. Properties like this that ...

eduplace.com/math/mathsteps/6/g/index.html

Pi. There are many fascinating numbers in mathematics. One of the most
interesting number relationships that students can discover in geometry is that
the ratio ...

britton.disted.camosun.bc.ca/pi/piorigin/piorigin.html

You know what 'PI' is ... it's a number with the value 3.14, and it's used to find the
circumference and area of a circle. But did you ever wonder where PI came ...