R, or r, a liquid consonant, being the seventeenth letter of our alphabet. Its sound is formed by a guttural ex-
Rabbetting. trusion of breath vibrated through the mouth, with a sort of quivering motion of the tongue drawn from the teeth, and con-
cated with the tip a little elevated towards the palate. In Greek words it is frequently aspirated with an h after it, as in rhapsody, rhetoric, and so forth; otherwise it is always followed by a vowel at the beginning of words and syllables.

In the notes of the ancients, R, or RO, signifies Roma, R. C. Romana civitas; R. G. C. rei gerendæ causa; R. F. E. D. recte factum et dictum; R. G. F. regis filius; R. P. res publica, or Romani principes, and R. R. R. F. F. F. res Romana ruet ferro, fame, flamma. Used as a numeral, R anciently stood for 80; and with a dash over it thus \bar{R}, for 80,000; but the Greek \rho, \rho', with a small mark over it, signified 100; with the same mark under it, it denoted 1000 \times 10; thus \rho, signifies 100,000. In the Hebrew numeration \aleph denoted 200; and with two horizontal points over it 1000 \times 200; thus \aleph = 200,000. In the prescriptions of physicians, R or R stands for recipe, that is, "take."