Akademik

r
1.
n. (also r) (pl. Rs or R's) the eighteenth letter of the alphabet.
Phrases and idioms:
the r months the months with r in their names (September to April) as the season for oysters.
2.
abbr. (also R.)
1 Regina (Elizabeth R).
2 Rex.
3 River.
4 (also
Usage:
) registered as a trademark.
5 (in names of societies etc.) Royal.
6 Chess rook.
7 Railway.
8 rand.
9 Regiment.
10 Reacuteaumur.
11 radius.
12 roentgen.

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R
(ɑː(r))
the eighteenth letter of the modern and seventeenth of the ancient Roman alphabet, is derived through early Greek egrho1, egrho2 from the Phoenician

Useful english dictionary. 2012.