- Rho (letter)
Rho (uppercase Ρ, lowercase ρ or Unicode|ϱ) is the 17th letter of the
Greek alphabet. In the system of Greek numeralsit 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.
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 orthographya rho at the beginning of a word is conventionally written with a rough breathing (equivalent to "h") — polytonic|ῥ — and a double rho within a word is written with a smooth breathing over the first rho and a rough breathing over the second — polytonic|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 Unicode|ῥῶ (polytonic) or ρω/ρο (monotonic).
Letters that arose from rho include Roman
Rand Cyrillic Er (Р).
Common notational uses
The characters Ρ, ρ and Unicode|ϱ are also used outside its Greek alphabetical context in
Science, and Mathematics.
**to represent the
Radiusin a system of spherical polar coordinates
**to represent the
correlation coefficientof a population parameter
**to represent the
Spectral radiusof a matrix denoted as
**to represent a
Economicsto represent the discount rate of future pence cash flows
Molecular Biologyto represent the Rho protein responsible for termination of RNA synthesis. In such occasions, it is often represented as unicode|ϱ ("rho symbol" U+03F1), to avoid confusion with the Latin letter "p"
LaTeX, the symbols are
**The lower-case rho "ρ" has a special meaning in the
APL programming language
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Rho — may refer to: NOTOC *Rho (letter), a letter of the Greek alphabet, upper case Ρ, lower case ρymbols;in mathematics * Spectral radius in a spherical coordinate system;in physics * Density of a material * Volume charge density * Resistivity of a… … Wikipedia
Rho — Das Rho (griechisches Neutrum Ρω, Majuskel Ρ, Minuskel ρ oder ϱ) ist der 17. Buchstabe des griechischen Alphabets und hat nach dem milesischen Prinzip einen numerischen Wert von 100. Am Anfang eines altgriechischen Wortes ist es immer… … Deutsch Wikipedia
rho|ta|cism — «ROH tuh sihz uhm», noun. an excessive use, mispronunciation, or substitution of the sound represented by r in English. ╂[< New Latin rhotacismus < Greek rhōtakízein overuse the letter rhô rho] … Useful english dictionary
rho — [rō] n. [Gr rhō < Sem: cf. Heb rosh] the seventeenth letter of the Greek alphabet (Ρ, ρ) … English World dictionary
rho — ► NOUN ▪ the seventeenth letter of the Greek alphabet (P, ), transliterated as ‘r’ or ‘rh’. ORIGIN Greek … English terms dictionary
rho|dop|sin — «roh DOP sihn», noun. a purplish red protein pigment that is sensitive to light, found in the rods of the retina of the eye; visual purple: »Rhodopsin was found to be the visual pigment in all vertebrates from the primitive lamprey to man… … Useful english dictionary
Rho Psi — The Rho Psi Society (ΡΨ) is an honorary fraternity Greek letter fraternity. Although founded as a student society, it is no longer active at the collegiate level. The objectives of the Society are to promote and perpetuate friendship among… … Wikipedia
rho — /roh/, n., pl. rhos. 1. the 17th letter of the Greek alphabet (P). 2. the consonant sound represented by this letter. [1350 1400; ME < Gk rhô] * * * … Universalium
letter — I (New American Roget s College Thesaurus) n. character, symbol; cuneiform, hieroglyphic; capital, majuscule; small letter, minuscule; consonant, vowel, digraph, diphthong; missive, note. See writing, communication. II (Roget s IV) n. 1. [A unit… … English dictionary for students
letter of the alphabet — noun the conventional characters of the alphabet used to represent speech his grandmother taught him his letters • Syn: ↑letter, ↑alphabetic character • Derivationally related forms: ↑letter (for: ↑letter) … Useful english dictionary