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# Rho (letter)

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 Title: Rho (letter) Author: World Heritage Encyclopedia Language: English Subject: Collection: Publisher: World Heritage Encyclopedia Publication Date:

### Rho (letter)

For other uses, see Rho (disambiguation).

Rho (glyph.

## 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 — ῤῥ rrh — 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).

### Other alphabets

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

### Mathematics and science

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 theology, it is used to sometimes denote the crucifixion of Jesus.

• In computer programming
• For LaTeX, the symbols are \rho ($\rho$), and \varrho ($\varrho$) (note: \Rho is not defined by default)
• The lower-case rho "ρ" has a special meaning in the APL programming language

### 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.[1]

## Character encodings

• Greek Rho symbols

• Coptic Ro

• Technical 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.