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There is no evidence for the following statement, especially with regard to foreign words.
Liddell & Scott ( A Greek-English Lexicon , 4th ed., 1855) list ᾿Ρᾶρος, ᾿Ράριος with Spiritus lenis, but also mention ῾Ράρος (with Spiritus asper) in the former, and write for the letter Rho: "Ρ, ρ [...] C. if ρ begins a word, it takes the rough breathing, except only in ῾Ράρος and ᾿Ράριος: though indeed in Aeol. Ρ was never aspirated ". In some digitized works it is similar ( LSJ, A Greek-English Lexicon & LS, An Intermediate Greek-English Lexicon have "Ρ̓ᾶρος" and "*) ra = ros", i.e. capitalized r with Spiritus lenis).
For names like Raphael, a Greek origin * ᾿Ραφαήλ (with Spiritus lenis) instead of ῾Ραφαήλ (with Spiritus asper) would be conceivable, which could possibly also fit better with Hebrew. Liddell & Scott do not list the word - possibly because it is too young - i.e. H. the statement by Liddell & Scott with the two exceptions is not necessarily correct for later periods.
At the beginning of an ancient Greek word it is always aspirated / breathed e.g. B. ῥέω (rhéō) I flow .
In surveying, the conversion factor between radians and other angular dimensions is denoted with a small rho: ρ = 180 / π for degrees, ρ = 200 / π for gons, ... It is used, for example, in formulas such as α / ρ = b / r, which outside of surveying, the ratio of central angle and arc is usually written as α = b / r.
In linguistics, the sound change to r is called Rhotazism .