From Wikipedia, the free encyclopedia

Look up Π, π in Wiktionary, the free dictionary.

Greek alphabet
Αα Alpha	Νν Nu
Ββ Beta	Ξξ Xi
Γγ Gamma	Οο Omicron
Δδ Delta	Ππ Pi
Εε Epsilon	Ρρ Rho
Ζζ Zeta	Σσ Sigma
Ηη Eta	Ττ Tau
Θθ Theta	Υυ Upsilon
Ιι Iota	Φφ Phi
Κκ Kappa	Χχ Chi
Λλ Lambda	Ψψ Psi
Μμ Mu	Ωω Omega
Obsolete letters
Ϝϝ Digamma	Ϙϙ Qoppa
Ϛϛ Stigma	Ϡϡ Sampi
Ϻϻ San	Ϸϸ Sho
Greek diacritics

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

In Modern Greek, the name of the letter is pronounced /pi/; in modern English, it is pronounced /paɪ/, in particular when referring to the mathematical constant (see below). In words, it is pronounced /p/. In Modern Greek, the sequence of letters μπ represents the /mb/ sound, as in boy (the second letter of the Greek alphabet is now pronounced /v/ as in very).

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

• The product operator in mathematics, indicated with capital pi notation ∏ (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.
• In legal shorthand, it represents a plaintiff.

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. The letter "π" is the first letter of the Greek words "περιφέρεια" 'periphery' and "περίμετρος" 'perimeter', i.e. the circumference.
• Radian (π=180 degrees)
• 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
• The natural projection on the tangent bundle on a manifold.

"Variant pi" or "pomega" ( or ϖ) is a glyph variant of lower case pi sometimes used in technical contexts as though it were a lower-case omega with a macron, though historically it is simply a cursive form of pi. It is used as a symbol for

• The angular frequency of a wave in fluid dynamics (angular frequency is usually represented by ω but this may be confused with vorticity in a fluid dynamics context).
• The longitude of pericenter in celestial mechanics. [1]
• Comoving distance in cosmology. [2]

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.