# Rho (letter): Wikis

Note: Many of our articles have direct quotes from sources you can cite, within the Wikipedia article! This article doesn't yet, but we're working on it! See more info or our list of citable articles.

# Encyclopedia

 Greek alphabet Obsolete letters Other characters Αα Alpha Νν Nu Ββ Beta Ξξ Xi Γγ Gamma Οο Omicron Δδ Delta Ππ Pi Εε Epsilon Ρρ Rho Ζζ Zeta Σσς 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 Digamma Qoppa San Sampi Stigma Sho Heta Greek diacritics

Rho (uppercase Ρ, lowercase ρ or ϱ), pronounced /ˈroʊ/ in English, is the 17th letter of the Greek alphabet. In the system of Greek numerals it has a value of 100. It is derived from Semitic Rêš "head" (see Resh). Its uppercase form is not to be confused with the Roman letter P, however both are typeset using the same glyph.

The letter Rho has religious significance within Christianity. When fused within a single typespace with the Greek letter Chi, it forms the labarum, which is used to represent Jesus Christ.

Rho is generally classed as a liquid (together with lambda and sometimes the nasals mu and nu), which has important implications for morphology. It is pronounced similarly to the letter r in languages with a Latin-derived alphabet. In polytonic orthography a rho at the beginning of a word is conventionally written with a rough breathing (equivalent to h) — — and a double rho within a word is written with a smooth breathing over the first rho and a rough breathing over the second — ῤῥ — apparently reflecting an aspirated or voiceless pronunciation in Ancient Greek, hence the various Greek-derived English words which start with rh or contain rrh. The name of the letter is written in Greek as ῥῶ (polytonic) or ρω/ρο (monotonic).

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

Former Rhode Scholars are entitled to use the Greek letter rho as a designation of their status. When used, the symbol should precede the name. [1]

## Common notational uses

The characters Ρ, ρ and ϱ are also used outside its Greek alphabetical context in science and mathematics.

• 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 ϱ ("rho symbol" U+03F1), to avoid confusion with the Latin letter p
• In ecology to represent the population damping ratio where ρ = λ1 / |λ2|.
• In programming
• For LaTeX, the symbols are P (Ρ), \rho (ρ), and \varrho ($\varrho$)
• The lower-case rho ρ has a special meaning in the APL programming language

## Computing

In Unicode, the upper and lower case are encoded at U+03A1 and U+03C1 respectively.