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
...

wiki.c2.com/?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.geom.uiuc.edu/~huberty/math5337/groupe/digits.html

100,000 Digits of Pi Pi Logo.
3.141592653589793238462643383279502884197169399375105820974944592307816406286
...

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
...

mathforum.org/dr.math/faq/faq.pi.html

What is pi ( )? Who first used pi? How do you find its value? What is it for? How
many digits is it? By definition, pi is the ratio of the circumference of a circle to its ...

www.math.rutgers.edu/~cherlin/History/Papers2000/wilson.html

The ratio of pi to 3 is very close to the ratio of 111 to 106. In other words, pi/3 =
111/106 approximately; solving for pi, we find pi = 3.1415094... (Tsaban, 78).

www.math.hmc.edu/funfacts/ffiles/10004.5.shtml

Pi is the ratio of the circumference of a circle to its diameter. It is known to be
irrational and its decimal expansion therefore does not terminate or repeat. The
first ...