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
...

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.mathgoodies.com/lessons/vol2/circumference.html

Pi is the ratio of the circumference of a circle to the diameter. Thus, for any circle,
if you divide the circumference by the diameter, you get a value close to Pi .

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
...

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.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).

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 ...

setosa.io/ev/pi/

The last line in the article is pointing out that we could've just as easily have used
the ratio C/R (circumference over radius) in the place of pi in almost every ...

www.scientificamerican.com/article/let-s-use-tau-it-s-easier-than-pi/

Jun 25, 2014 ... The crux of the argument is that pi is a ratio comparing a circle's circumference
with its diameter, which is not a quantity mathematicians ...