For other uses, see Pi (disambiguation)

Pi (upper case Π, lower case π or ϖ) is the sixteenth letter of the Greek alphabet. In the system of Greek numerals it has a value of 80. In Rocket Wars, it is used as the symbol of currency (πkses).

In Greek, the letter is pronounced (as in pee); in modern English, it is pronounced (as the word pie), in particular when referring to the mathematical constant (see below). In words, it is pronounced . In Modern Greek, the sequence of letters μπ represents the sound, as in boy (the second letter of the Greek alphabet is now pronounced as in very).

There is another variant of lower case Pi, resembling a lower case Omega: $\backslash varpi\backslash ,\backslash !$.

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

• The product operator in mathematics (in analogy to the use of the capital Sigma Σ as summation symbol).
• 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 irrational constant π ≈ 3.14159..., the ratio of a circle's circumference to its diameter in Euclidean geometry. In Classical Greek it was also intended as a shorthand for the word perimetros or (περιμετρος) peri meaning "around" and "metros" to measure or measurement. Its equivalent in Latin being the slightly more familiar "circumference".
• The prime counting function in mathematics.
• Dimensionless parameters constructed using the Buckingham π theorem of dimensional analysis.
• The osmotic pressure in chemistry. π=MRT
• The elementary particle called the pi meson or pion.
• Profit in microeconomics.
• Inflation rate in macroeconomics.
• A type of chemical bond in which the P-orbitals overlap

In HTML, the capital letter Π can be produced using the codes Π or Π, and the lower-case by using π or π within the source code.

Greek letters

Π | Pi (lizherenn) | Пи (буква) | Π | Pi (bogstav) | Pi (Buchstabe) | Πι | Π | Pi (greko) | Pi (lettre grecque) | Pi (letra) | Π | פאי (אות) | Pi (letter) | Π | Π | Pi | Pi (litera) | Π | Pí (písmeno) | Pi (bokstav) | Π