R /(är)/

R
  1. R, the eighteenth letter of the English alphabet, is a vocal consonant. It is sometimes called a semivowel, and a liquid. See Guide to Pronunciation, §§ 178, 179, and 250-254.

Phrases & Compounds
The three Rs
a jocose expression for reading, (w)riting, and (a)rithmetic, -- the fundamentals of an education.