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Pi (letter)

Pi (Π π) is the 16th letter of the Greek alphabet and has a numeric value of 80.

The upper-case letter Π is used as a symbol for:

In mathematics, the product operation.
In textual criticism, Codex Petropolitanus, a 9th century, uncial codex of the Gospels, now located in St. Petersburg, Russia.

The lower-case letter π is used as a symbol for:

In economics, profit.
In mathematics, the constant pi, which is the ratio of the circumference to the diameter of a circle.
In number theory, the function π(x) is the number of primes that are less than or equal to x.
In particle physics, π⁰, π⁺ and π^- are three forms of pi meson.