Pi (letter)

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Pi (; uppercase ?, lowercase ?; Greek: ?? [pi]) is the sixteenth letter of the Greek alphabet, representing the sound [p]. In the system of Greek numerals it has a value of 80. It was derived from the Phoenician letter Pe (). Letters that arose from pi include Cyrillic Pe (?, ?), Coptic pi (?, ?), and Gothic pairthra (?).

Video Pi (letter)

Symbol

The upper-case letter ? 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 ? 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 osmotic pressure in chemistry.

The lower-case letter ? is used as a symbol for:

• The mathematical real transcendental (and thus irrational) constant ? = 3.14159..., the ratio of a circle's circumference to its diameter in Euclidean geometry. The letter "?" is the first letter of the Greek words "??????????" 'periphery' and "??????????" 'perimeter', i.e. the circumference.
• The prime-counting function in mathematics.
• Homotopy groups in algebraic topology.
• Dimensionless parameters constructed using the Buckingham ? theorem of dimensional analysis.
• The hadron called the pi meson or pion.
• Economic profit in microeconomics.
• Inflation rate in macroeconomics.
• A type of chemical bond in which the P-orbitals overlap, called a pi bond.
• The natural projection on the tangent bundle on a manifold.
• The unary operation of projection in relational algebra.
• Policy in reinforcement learning.

Maps Pi (letter)

History

An early form of pi was , appearing almost like a gamma with a hook.

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Variant pi

Variant pi or "pomega" (${\displaystyle \varpi \,\!}$ or ?) 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, with its legs bent inward to meet. It is used as a symbol for:

• Angular frequency of a wave in fluid dynamics (angular frequency is usually represented by ${\displaystyle \omega }$ but this may be confused with vorticity in a fluid dynamics context).
• Longitude of pericenter in celestial mechanics.
• Comoving distance in cosmology.
• Single-scattering albedo in radiative transfer.
• Mean fitness of a population in biology.

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Character encodings

The various forms of pi are present in Unicode as:

• U+03A0 ? GREEK CAPITAL LETTER PI (HTML Π · Π)
• U+03C0 ? GREEK SMALL LETTER PI (HTML π · π)
• U+03D6 ? GREEK PI SYMBOL (HTML ϖ · ϖ)
• U+220F ? N-ARY PRODUCT (HTML ∏ · ∏)
• U+1D28 ? GREEK LETTER SMALL CAPITAL PI (HTML ᴨ)
• U+1D70B ? MATHEMATICAL ITALIC SMALL PI (HTML 𝜋)
• U+1D6D1 ? MATHEMATICAL BOLD SMALL PI (HTML 𝛑).

Character encodings tables

• Greek / Coptic Pi

• Mathematical Pi

These characters are used only as mathematical symbols. Stylized Greek text should be encoded using the normal Greek letters, with markup and formatting to indicate text style.

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See also

• ?, ? - Pe (Cyrillic)
• ?, ? - Er (Cyrillic)
• P, p - Pe (Latin)
• Greek letters used in mathematics, science, and engineering#?? (pi)
• Pilcrow - an unrelated but similar looking glyph (¶)

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References

Source of article : Wikipedia