Rho

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For other uses, see Rho (disambiguation).

Rho (/ˈr/; uppercase Ρ, lowercase ρ or ϱ) 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 Phoenician res.svg. Its uppercase form is not to be confused with the Latin letter P, although both are typeset using the same glyph.

Uses[edit]

The Greek alphabet on a black figure vessel, with an R-shaped rho.

Greek[edit]

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 that start with rh or contain rrh.

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

Other alphabets[edit]

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

Mathematics and science[edit]

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|.

Chi Rho[edit]

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

Rhodes Scholars[edit]

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[edit]

Greek Rho[2][edit]

Character Ρ ρ
Unicode name GREEK CAPITAL LETTER RHO GREEK SMALL LETTER RHO GREEK CAPITAL LETTER RHO WITH DASIA GREEK SMALL LETTER RHO WITH DASIA GREEK SMALL LETTER RHO WITH PSILI
Encodings decimal hex decimal hex decimal hex decimal hex decimal hex
Unicode 929 U+03A1 961 U+03C1 8172 U+1FEC 8165 U+1FE5 8164 U+1FE4
UTF-8 206 161 CE A1 207 129 CF 81 225 191 172 E1 BF AC 225 191 165 E1 BF A5 225 191 164 E1 BF A4
Numeric character reference Ρ Ρ ρ ρ Ῥ Ῥ ῥ ῥ ῤ ῤ
Named character reference Ρ ρ
DOS Greek 144 90 168 A8
DOS Greek-2 199 C7 235 EB
Windows 1253 209 D1 241 F1
TeX \rho

Greek Rho symbols[edit]

Character ϱ ϼ
Unicode name GREEK RHO SYMBOL GREEK RHO WITH STROKE SYMBOL GREEK LETTER SMALL CAPITAL RHO GREEK SUBSCRIPT SMALL LETTER RHO CHI RHO
Encodings decimal hex decimal hex decimal hex decimal hex decimal hex
Unicode 1009 U+03F1 1020 U+03FC 7465 U+1D29 7528 U+1D68 9767 U+2627
UTF-8 207 177 CF B1 207 188 CF BC 225 180 169 E1 B4 A9 225 181 168 E1 B5 A8 226 152 167 E2 98 A7
Numeric character reference ϱ ϱ ϼ ϼ ᴩ ᴩ ᵨ ᵨ ☧ ☧
TeX \varrho

Coptic Ro[edit]

Character
Unicode name COPTIC CAPITAL LETTER RO COPTIC SMALL LETTER RO COPTIC SYMBOL CHI RHO
Encodings decimal hex decimal hex decimal hex
Unicode 11426 U+2CA2 11427 U+2CA3 11497 U+2CE9
UTF-8 226 178 162 E2 B2 A2 226 178 163 E2 B2 A3 226 179 169 E2 B3 A9
Numeric character reference Ⲣ Ⲣ ⲣ ⲣ ⳩ ⳩

Technical Symbol[edit]

Character
Unicode name APL FUNCTIONAL SYMBOL RHO
Encodings decimal hex
Unicode 9076 U+2374
UTF-8 226 141 180 E2 8D B4
Numeric character reference ⍴ ⍴

Mathematical Rho[edit]

Character 𝚸 𝛒 𝛠 𝛲 𝜌
Unicode name MATHEMATICAL BOLD
CAPITAL RHO
MATHEMATICAL BOLD
SMALL RHO
MATHEMATICAL BOLD
RHO SYMBOL
MATHEMATICAL ITALIC
CAPITAL RHO
MATHEMATICAL ITALIC
SMALL RHO
Encodings decimal hex decimal hex decimal hex decimal hex decimal hex
Unicode 120504 U+1D6B8 120530 U+1D6D2 120544 U+1D6E0 120562 U+1D6F2 120588 U+1D70C
UTF-8 240 157 154 184 F0 9D 9A B8 240 157 155 146 F0 9D 9B 92 240 157 155 160 F0 9D 9B A0 240 157 155 178 F0 9D 9B B2 240 157 156 140 F0 9D 9C 8C
UTF-16 55349 57016 D835 DEB8 55349 57042 D835 DED2 55349 57056 D835 DEE0 55349 57074 D835 DEF2 55349 57100 D835 DF0C
Numeric character reference 𝚸 𝚸 𝛒 𝛒 𝛠 𝛠 𝛲 𝛲 𝜌 𝜌
Character 𝜚 𝜬 𝝆 𝝔 𝝧
Unicode name MATHEMATICAL ITALIC
RHO SYMBOL
MATHEMATICAL BOLD ITALIC
CAPITAL RHO
MATHEMATICAL BOLD ITALIC
SMALL RHO
MATHEMATICAL BOLD ITALIC
RHO SYMBOL
MATHEMATICAL SANS-SERIF
BOLD CAPITAL RHO
Encodings decimal hex decimal hex decimal hex decimal hex decimal hex
Unicode 120602 U+1D71A 120620 U+1D72C 120646 U+1D746 120660 U+1D754 120679 U+1D767
UTF-8 240 157 156 154 F0 9D 9C 9A 240 157 156 172 F0 9D 9C AC 240 157 157 134 F0 9D 9D 86 240 157 157 148 F0 9D 9D 94 240 157 157 167 F0 9D 9D A7
UTF-16 55349 57114 D835 DF1A 55349 57132 D835 DF2C 55349 57158 D835 DF46 55349 57172 D835 DF54 55349 57191 D835 DF67
Numeric character reference 𝜚 𝜚 𝜬 𝜬 𝝆 𝝆 𝝔 𝝔 𝝧 𝝧
Character 𝞀 𝞎 𝞠 𝞺 𝟈
Unicode name MATHEMATICAL SANS-SERIF
BOLD SMALL RHO
MATHEMATICAL SANS-SERIF
BOLD RHO SYMBOL
MATHEMATICAL SANS-SERIF
BOLD ITALIC CAPITAL RHO
MATHEMATICAL SANS-SERIF
BOLD ITALIC SMALL RHO
MATHEMATICAL SANS-SERIF
BOLD ITALIC RHO SYMBOL
Encodings decimal hex decimal hex decimal hex decimal hex decimal hex
Unicode 120704 U+1D780 120718 U+1D78E 120736 U+1D7A0 120762 U+1D7BA 120776 U+1D7C8
UTF-8 240 157 158 128 F0 9D 9E 80 240 157 158 142 F0 9D 9E 8E 240 157 158 160 F0 9D 9E A0 240 157 158 186 F0 9D 9E BA 240 157 159 136 F0 9D 9F 88
UTF-16 55349 57216 D835 DF80 55349 57230 D835 DF8E 55349 57248 D835 DFA0 55349 57274 D835 DFBA 55349 57288 D835 DFC8
Numeric character reference 𝞀 𝞀 𝞎 𝞎 𝞠 𝞠 𝞺 𝞺 𝟈 𝟈

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.

See also[edit]

References[edit]

  1. ^ "Oxford University Calendar: Notes on Style". Oxford University Gazette. 2011-03-03. Retrieved 2011-09-08. 
  2. ^ Unicode Code Charts: Greek and Coptic (Range: 0370-03FF)