# pi

^{1}pi

*noun*\ˈpī\

*plural*

**pis**\ˈpīz\

## Definition of *PI*

**:**the 16th letter of the Greek alphabet — see alphabet table

*a*

**:**the symbol π denoting the ratio of the circumference of a circle to its diameter

*b*

**:**the ratio itself

**:**a transcendental number having a value rounded to eight decimal places of 3.14159265

## Origin of *PI*

*pei,*of Semitic origin; akin to Hebrew

*pē*pe

^{2}pi

*noun*\ˈpī\

*plural*

**pies**

## Definition of *PI*

**:**type that is spilled or mixed

**:**a pi character or matrix

## Variants of *PI*

**pi**also

**pie**\ˈpī\

## Origin of *PI*

^{3}pi

*verb*

**pied**

**pi·ing**

*or*

**pie·ing**

## Definition of *PI*

**:**to spill or throw (type or type matter) into disorder

**:**to become pied

## Variants of *PI*

**pi**also

**pie**

## First Known Use of *PI*

^{4}pi

*adjective*

## Definition of *PI*

**:**not intended to appear in final printing <

*pi*lines>

**:**capable of being inserted only by hand <

*pi*characters>

## Variants of *PI*

**pi**also

**pie**

## First Known Use of *PI*

## PI

*abbreviation*

## Definition of *PI*

## pi

*noun*

*(Concise Encyclopedia)*

In mathematics, the ratio of the circumference of a circle to its diameter. An irrational number (*see also* transcendental number), it has an approximate value of 3.14, but its exact value must be represented by a symbol, the Greek letter . Pi is used in calculations involving lengths, areas, and volumes of circles, spheres, cylinders, and cones. It also arises frequently in problems dealing with certain periodic phenomena (e.g., motion of pendulums, alternating electric currents). By the end of the 20th century, computers had calculated pi to more than 200 billion decimal places.

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