so called from the words of the commission, quorum A.B. unum esse voluimus ("of whom we will that A.B. be one"); thus rendering it necessary that certain individuals (said to be of the quorum) should be present at the transaction of business. R, a liquid consonant, being the eighteenth letter of the English alphabet. Its sound is formed by a guttural extrusion of breath vibrated through the mouth, with a sort of quivering motion of the tongue drawn back from the teeth, and advanced with the tip a little elevated towards the palate. It is convertible with the letters l, n, m, and s. It is apt to place itself at one time before, at another time after a vowel, and is liable to disappear from the neighborhood of several consonants.

In the notes of the ancients, R or RO signifies Roma. R. C. Romana civitas; R. G. C. rei gerendae causa; R. F. E.D. rete factum et dictum; R. G. F. regis filius; R. P. res publica, or Romani principes, and R. R. R. F. F. F. res Romanae ruet ferro, fane, flamma. (See Abbreviations.) Used as a numeral, R anciently stood for 80; and with a dash over it, thus R, for 80,000; but the Greek R, ῥ, with a small mark over it, signified 100; with the same mark under it, denoted 1000 × 10; thus ῥ signifies 100,000. In the Hebrew numeration ῥ denoted 200; and with two horizontal points over it, thus ῥ, 1000 × 200 = 200,000.

In the prescriptions of physicians, R or ῥ stands for recipe, that is, "take."