Pi (letter)

Greek alphabet
Α α Alpha	Β β Beta
Γ γ Gamma	Δ δ Delta
Ε ε Epsilon	Ζ ζ Zeta
Η η Eta	Θ θ Theta
Ι ι Iota	Κ κ Kappa
Λ λ Lambda	Μ μ Mu
Ν ν Nu	Ξ ξ Xi
Ο ο Omicron	Π π Pi
Ρ ρ Rho	Σ σ Sigma
Τ τ Tau	Υ υ Upsilon
Φ φ Phi	Χ χ Chi
Ψ ψ Psi	Ω ω Omega
obsolete letters
Ϝ ϝ Digamma	Ϻ ϻ San
Ϙ ϙ Qoppa	Ϡ ϡ Sampi

Pi (upper case Π, lower case π) is the 16th letter of the Greek alphabet. In the system of Greek numerals it has a value of 80.

In Greek, the letter is pronounced /piː/; in English, though, it is pronounced /paɪː/ (as the word pie). In words, it is pronounced /p/. In Modern Greek, the sequence of letters μπ represents the /b/ sound, as in boy (the second letter of the Greek alphabet is now pronounced /v/ as in very).

There is another variant of lower case Pi, resembling a lower case Omega: ϖ.

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 π ≈ 3.14159, the ratio of a circle's circumference to its diameter.
• The prime counting function in mathematics.
• Dimensionless parameters constructed using the Buckingham Pi theorem of dimensional analysis.
• The elementary particle called the pi meson or pion.
• Profit in microeconomics.
• Inflation rate in macroeconomics.

See also: Pi (letter), 9th century, Alpha (letter), Beta (letter), Buckingham Pi theorem, Chi (Greek letter), Codex, Delta (letter)