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  1. Pi - Math is Fun

    Draw a circle with a diameter (all the way across the circle) of 1 ... Then the circumference (all the way around the circle) is 3.14159265... a number known as Pi

  2. Pi | Definition, Symbol, Number, History, Applications ...

    Dec 10, 2025 · Pi, in mathematics, is the ratio of the circumference of a circle to its diameter. Because pi is irrational (not equal to the ratio of any two whole numbers), its digits do not repeat, and an …

  3. Pi - Wikipedia

    The circumference of a circle is slightly more than three times as long as its diameter. The exact ratio is called π. π is commonly defined as the ratio of a circle 's circumference C to its diameter d: [3] The …

  4. What is Pi? | Pi Day

    Learn about the number pi, why it is important in math, and what it is used to calculate!

  5. Pi Symbol (π)

    The greek small letter π (pi) is a geometric constant approximately equal to 3.1416. The numeric value is equal to the length of any circle's circumference divided by its diameter.

  6. Pi

    Pi Pi (π) is the ratio of the circumference of a circle to its diameter. The value of pi is 3.14159..., an irrational number. Pi is a constant value. That is, the ratio of the circumference to the diameter is the …

  7. Pi (π)

    All things about Pi (π).The number π is a mathematical constant. It is defined as the ratio of a circle's circumference to its diameter, and it also has various equivalent definitions. It appears in many …