U, or u, the 20th letter and 5th vowel of our alphabet, is formed in the voice by a round configuration of the lips, and a greater extrusion of the under one than in forming the letter o, and the tongue is also more cannulated. The sound is short in curst, must, tun, tub; but is lengthened by a final e, as in tune, tube, &c. In some words it is rather acute than long; as in brute, flute, lute, &c. It is mostly long in polysyllables; as in union, curious, &c. but in some words it is obscure, as in nature, venture, &c. This letter in the form of V or v, is properly a consonant, and as such is placed before all the vowels; as in vacant, venal, vibrate, &c. Though the letters v and u had always two sounds, they had only the form v till the beginning of the fourth century, when the other form was introduced, the inconvenience of expressing two different sounds by the same letter having been observed long before. In numerals V stands for five; and with a dash added at top, thus , it signifies 5000.
In abbreviations, amongst the Romans, V. A. flood for veterrani assignati; V. B. viro bono; V. B. A. viri boni arbitrari; V. B. F. viri bona fidei; V. C. viri consularis; V. C. C. F. vale, conjus charissime, feliciter; V. D. D. voto dedicatur; V. G. verbi gratia; Vir. Ve. virgo vestalis; VL. videlicet; V. N. quinto nonarum.