U (ū), the twenty-first letter of the English
alphabet, is a cursive form of the letter V, with which it was formerly
used interchangeably, both letters being then used both as vowels and
consonants. U and V are now, however, differentiated, U being used only as
a vowel or semivowel, and V only as a consonant. The true primary vowel
sound of U, in Anglo-Saxon, was the sound which it still retains in most of
the languages of Europe, that of long oo, as in tool, and
short oo, as in wood, answering to the French ou in
tour. Etymologically U is most closely related to o, y
(vowel), w, and v; as in two, duet,
dyad, twice; top, tuft; sop, sup;
auspice, aviary. See V, also O and Y.
See Guide to Pronunciation, §§ 130-144.