Rho
Greek alphabet | ||||||||||||||||||||||||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
||||||||||||||||||||||||||||||||||||||||||||||||
History | ||||||||||||||||||||||||||||||||||||||||||||||||
Use in other languages | ||||||||||||||||||||||||||||||||||||||||||||||||
Related topics | ||||||||||||||||||||||||||||||||||||||||||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||
Rho /ˈroʊ/ (uppercase Ρ, lowercase ρ or ϱ; Greek: ῥῶ) 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, Ρ, as the distinct Latin letter P; the two letters have different Unicode encodings.
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 (ῥ 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). 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 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 and ϱ 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 (ρ)
- Resistivity (ρ)
- Rho meson (ρ+, ρ−, ρ0)
- General quantum states
- Hammett Equation, ρ 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 denoted as
- The plastic number
- The prime constant
- The sensitivity to interest rates of a pricing function
- The expected return of a given policy () in reinforcement learning, denoted
- 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 molecular biology to represent the Rho family of GTPases, important for cytoskeletal dynamic regulation.
- In ecology to represent the population damping ratio where ρ = λ1 / |λ2|.
- In computer programming
- For LaTeX, the symbols are
\rho
(), and\varrho
() (note:\Rho
is not defined by default) - The lower-case rho "⍴" means reshape in the APL programming language, and by extension also queries shape
- The lower-case rho "ρ" is used for the unary rename operation in relational algebra
- For LaTeX, the symbols are
- 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.
Rho with stroke (ϼ)[]
The rho with a stroke through its tail is used for abbreviations involving rho, most notably in γϼ for γράμμα as a unit of measurement.[1]
Character encodings[]
Greek rho[2][]
Preview | Ρ | ρ | Ῥ | ῥ | ῤ | |||||
---|---|---|---|---|---|---|---|---|---|---|
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[]
Preview | ϱ | ϼ | ᴩ | ᵨ | ☧ | |||||
---|---|---|---|---|---|---|---|---|---|---|
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 |
☧ |
☧ |
Named character reference | ϱ, ϱ | |||||||||
TeX | \varrho |
Coptic ro[]
Preview | Ⲣ | ⲣ | ⳩ | |||
---|---|---|---|---|---|---|
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 |
⳩ |
⳩ |
Functional symbol[]
Preview | ⍴ | |
---|---|---|
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[]
Preview |
---|