Rho


Rho 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, 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, and a double rho within a word is written with a smooth breathing over the first rho and a rough breathing over the second. 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 or ρω/.

Other alphabets

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

Mathematics and science

The characters ρ and ϱ are also conventionally used outside the Greek alphabetical context in science and mathematics.
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.

Character encodings

Greek rhoUnicode Code Charts: https://www.unicode.org/charts/PDF/U0370.pdf [Greek and Coptic (Range: 0370-03FF)]

Greek rho symbols

Coptic ro

Functional 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.