Pi (letter)
From Wikipedia, the free encyclopedia.

Pi (Π π) is the 16th letter of the Greek alphabet and has a numeric value of 80. In words it is pronounced /p/.

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

• The product operator in mathematics (similar to a series).
• 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:

• The mathematical constant &pi  3.14159, being the ratio of a circle's circumference to its diameter.
• The prime counting function in mathematics.
• The pi mesons in particle physics.
• Profit in economics.

The original article can be found at: http://en.wikipedia.org/wiki/Pi_(letter).
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