Rho (letter)

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Rho (letter)

Rho (uppercase ?, lowercase ? or ) is the 17th letter of the Greek alphabet

Greek alphabet

The Greek alphabet is a set of twenty-four letters that has been used to write the Greek language since the late 9th century BC or early 8th century BCE....
. In the system of Greek numerals

Greek numerals

Greek numerals are a numeral system using letters of the Greek alphabet. They are also known by the names Milesian numerals, Alexandrian numerals, or alphabetic numerals....
it has a value of 100. It is derived from Semitic

Proto-Canaanite alphabet

The Proto-Canaanite alphabet is a consonantal alphabet of twenty-two Acrophony glyphs, found in Levantine texts of the Late Bronze Age , by convention taken to last until a cut-off date of 1050 BC, after which it is called Phoenician alphabet....
Rêš "head" (see Resh

Resh

Resh is the twentieth letter of many Semitic History of the alphabet, including Phoenician language, Aramaic language, Hebrew language and Arabic alphabet ....
). Its uppercase form is not to be confused with the Roman letter P

P is the sixteenth letter of the modern Latin alphabet. Its name in English language is pronounced pee ....
.

The letter Rho has significant religious significance within Christianity. When fused within a single typespace with the Greek letter Chi

Chi (letter)

Chi is the 22nd letter of the Greek alphabet, pronounced as [kai] in English. Its value in Ancient Greek was an aspirated voiceless velar plosive ....
, it is called the labarum

Labarum

For the article about the "PX" symbol see Chi RhoThe Labarum was a typographic ligature formed from Chi and Rho , which had particular symbolic significance to the Roman Empires, Ancient Greece, and to the Christianity of Late Antiquity in general....
and used to represent the person of Jesus Christ.

Rho is generally classed as a liquid

Liquid consonant

Liquid consonants, or liquids, are trill consonants, tap consonant, or approximant consonants that are not classified as semivowels because they do not correspond phonetically to specific vowels ....
(together with lambda and sometimes the nasals mu

Mu (letter)

Mu is the 12th letter of the Greek alphabet. In the system of Greek numerals it has a value of 40. Mu was derived from the Egyptian hieroglyphic symbol for water which had been simplified by the Phoenicians and named after their word for water, to become Mem ....
and nu

Nu (letter)

Nu , is the 13th letter of the Greek alphabet. In the system of Greek numerals it has a value of 50. Its Latin Alphabet equivalent is N, though the lowercase resembles the Roman lowercase v....
), which has important implications for morphology

Morphology (linguistics)

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Rho (uppercase ?, lowercase ? or ) is the 17th letter of the Greek alphabet

Greek alphabet

The Greek alphabet is a set of twenty-four letters that has been used to write the Greek language since the late 9th century BC or early 8th century BCE....
. In the system of Greek numerals

Greek numerals

Proto-Canaanite alphabet

Resh

Chi (letter)

Chi is the 22nd letter of the Greek alphabet, pronounced as [kai] in English. Its value in Ancient Greek was an aspirated voiceless velar plosive ....
, it is called the labarum

Labarum

Liquid consonant

Mu (letter)

Nu (letter)

Morphology (linguistics)

Morphology is the identification, analysis and description of structure of words . While words are generally accepted as being the smallest units of syntax, it is clear that in most languages, words can be related to other words by rules....
. 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 — — apparently reflecting an aspirated or voiceless pronunciation in Ancient Greek

Ancient Greek

Ancient Greek is the historical stage in the development of the Greek language spanning across the Archaic Greece , Classical Greece , and Hellenistic civilization periods of ancient Greece and the classical antiquity....
, hence the various Greek-derived English words which start with rh or contain rrh. The name of the letter is written in Greek as (polytonic) or ??/?? (monotonic).

Letters that arose from rho include Roman R

R is the eighteenth letter of the modern Latin alphabet. Its name in English language is spelled ar ....
and Cyrillic Er

Er (Cyrillic)

eading=Cyrillic letter Er|Image=...
.

If a person is a former Rhodes Scholar, they are entitled to use the Greek letter rho. If used, the symbol should precede the name. (citation, http://www.ox.ac.uk/gazette/calendar/style.pdf)

Common notational uses

The characters ?, ? and are also used outside its Greek alphabetical context in Science

Science

In its broadest sense, science refers to any systematic knowledge or practice. In its more usual restricted sense, science refers to a system of acquiring knowledge based on scientific method, as well as to the organized body of knowledge gained through such research....
, and Mathematics

Mathematics

Mathematics is the study of quantity, structure, space, change, and related topics of pattern and form. Mathematicians seek out patterns whether found in numbers, space, natural science, computers, imaginary abstractions, or elsewhere....
.

In Physics
Physics

Physics is the natural science which examines basic concepts such as energy, force, and spacetime and all that derives from these, such as mass, charge, matter and its Motion ....

to represent Density
Density

The density of a material is defined as its mass per unit volume. The symbol of density is ....
to represent Momentum
Momentum

In classical mechanics, momentum is the product of the mass and velocity of an object . For more accurate measures of momentum, see the section Momentum#Modern definitions of momentum on this page....
to represent Resistivity
Resistivity

Electrical resistivity is a measure of how strongly a material opposes the flow of electric current. A low resistivity indicates a material that readily allows the movement of electrical charge....
to represent Charge density
Charge density

The linear, surface, or volume charge density is the amount of electric charge in a line , surface, or volume. It is measured in coulombs per metre , square metre , or cubic metre , respectively....

In Mathematics
Mathematics

Mathematics is the study of quantity, structure, space, change, and related topics of pattern and form. Mathematicians seek out patterns whether found in numbers, space, natural science, computers, imaginary abstractions, or elsewhere....

to represent the Radius
RADIUS

Remote Authentication Dial In User Service is a networking protocol that provides centralized access, authorization and accounting management for people or computers to connect and use a network service....
in a system of spherical polar coordinates
Coordinates (mathematics)

Coordinates are numbers which describe the location of points in a plane or in space. For example, the height above sea level is a coordinate which is useful for describing points near the surface of the earth....
to represent the correlation coefficient of a population parameter
to represent the Spectral radius
Spectral radius

In mathematics, the spectral radius of a matrix or a bounded linear operator is the supremum among the absolute values of the elements in its spectrum of a matrix, which is sometimes denoted by ρ....
of a matrix denoted as
to represent a Plastic number
Plastic number

In math, the plastic number is the unique real solution of the cubic equationand has the valuewhich is approximately 1.324717957244746025960908854 ....

In Economics
Economics

File:Ballard Farmers' Market - vegetables.jpgEconomics is the Social sciences that studies the Production theory basics, Distribution , and Consumption of Good and Service ....
to represent the discount rate of future pence cash flows

In Molecular Biology
Molecular biology

Molecular biology is the study of biology at a molecule level. The field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry....
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 Programming

For LaTeX
LaTeX

LaTeX is a document markup language and Word processor for the TeX typesetting program. Within the typesetting system, its name is styled as ....
, the symbols are P, \rho , and \varrho
The lower-case rho ? has a special meaning in the APL programming language
APL programming language

APL is an array programming language based on a notation invented in 1957 by Kenneth E. Iverson while at Harvard University. It originated as an attempt to provide consistent notation for the teaching and analysis of topics related to the application of computers....

Rho (letter)

Common notational uses

See also