Rho

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Rho (; uppercase ?, lowercase ? or ?; Greek: ??) is the 17th letter of the Greek alphabet. In the system of Greek numerals, it has a value of 100. It is derived from Phoenician letter res . Its uppercase form uses the same glyph, ?, as the distinct Latin letter P; the two letters have different Unicode encodings.

Video Rho

Uses

Greek

Rho is classed as a liquid consonant (together with lambda and sometimes the nasals mu and nu), which has important implications for morphology. In both Ancient and Modern Greek, it represents a trilled or tapped r.

In polytonic orthography, a rho at the beginning of a word is written with a rough breathing, equivalent to h (? rh), and a double rho within a word is written with a smooth breathing over the first rho and a rough breathing over the second (?? rrh). That apparently reflected an aspirated or voiceless pronunciation in Ancient Greek, which led to the various Greek-derived English words starting with rh or contain rrh.

The name of the letter is written in Greek as ?? (polytonic) or ??/?? (monotonic).

Other alphabets

Letters that arose from rho include Roman R and Cyrillic Er (?).

Mathematics and science

The characters ? and ? are also conventionally used outside the Greek alphabetical context in science and mathematics.

• In the physical sciences to represent:
  • Densities: mass density, air density or charge density (?)
  • Resistivity (?)
  • Rho meson (?⁺, ?^-, ?⁰)
  • General quantum states
  • Hammett Equation, ? is used to represent the reaction constant, this is independent of the position and nature of the substituents of the benzene ring.
• In mathematics to represent:
  • A length coordinate in polar, cylindrical, spherical, and toroidal coordinate systems, and toroidal and poloidal coordinates of the Earth's magnetic field.
  • The correlation coefficient of a population parameter
  • The spectral radius of a matrix ${\displaystyle A}$ denoted as ${\displaystyle \rho (A)}$
  • The plastic number
  • The 'prime constant' number
  • The sensitivity to interest rates of a pricing function
  • The expected return of a given policy (${\displaystyle \pi }$) in reinforcement learning, denoted ${\displaystyle \rho ^{\pi }}$
• In economics to represent the discount rate of future pence cash flows
• In molecular biology to represent the Rho protein responsible for termination of RNA synthesis. In such occasions, it is often represented as ? ("rho symbol" U+03F1), to avoid confusion with the Latin letter p
• In ecology to represent the population damping ratio where ? = ?1 / |?2|.
• In computer programming
  • For LaTeX, the symbols are \rho (${\displaystyle \rho }$), and \varrho (${\displaystyle \varrho }$) (note: \Rho is not defined by default)
  • The lower-case rho "?" has a special meaning in the APL programming language
• In statistics to represent Spearman's rank correlation coefficient, commonly known as Spearman's rho
• In options theory to represent the rate of change of a portfolio with respect to interest rates

Chi Rho

The letter rho overlaid with chi forms the Chi Rho symbol, used to represent Jesus Christ.

Rhodes Scholars

Former Rhodes Scholars are entitled to use the Greek letter rho as a designation of their status. When used, the symbol should precede the name.

Maps Rho

Character encodings

Greek Rho

Greek Rho symbols

Coptic Ro

Functional Symbol

Mathematical Rho

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

• ?, ? - Er (Cyrillic)
• R, r - Latin
• P, p - Latin

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References

Source of the article : Wikipedia