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The Greek letter used for the ratio of a circle's circumference to its diameter.
Also known as: Pi symbol, Greek letter pi, 3.14 symbol
Pi denotes the ratio of a circle's circumference to its diameter, approximately 3.14159. The letter was adopted for this purpose in the eighteenth century and popularised by Euler.
Denotes the ratio of a circle's circumference to its diameter, an irrational number beginning 3.14159.
Contexts: Mathematics
Was adopted for this ratio in the eighteenth century and became standard largely through Euler's use of it.
18th century onward · Contexts: Mathematics
In its capital form (Π) denotes a product over a series, a different operator that happens to share the letter.
Capital and lower-case pi are distinct operators, not stylistic variants.
Contexts: Mathematics
A horizontal bar resting on two downward strokes, the lower-case Greek letter pi.
The product operator is the capital form of this letter and a separate character from it, in the same way the summation sign relates to sigma.