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.