2. The close, curt, short, or stopped u; as in tub, butter, justice, unhung.
3. The middle u, resembling a short or quick oo; as in pull, pulpit, artful.
U forming a syllable by itself or U as naming itself is nearly equivalent in sound to you, and requires the article a, and not an, before it; as, a U, a union.
U sometimes borrows the sound of some other vowel; for bury is pronounced berry, and busy is pronounced bizzy. So in the derivatives, burial, buried, busied, busily, and the like.
The long or diphthongal u, commonly sounded as yu, or as ew in ewer,—or any equivalent diphthong or digraph, as ue, ui, eu, or ew.—when it follows r or rh, assumes the sound of slender o or oo; as in rude, rhubarb, rue, rueful, rheum, fruit, truth, brewer.
DIPHTHONGS BEGINNING WITH U.
U, in the proper diphthongs, ua, ue, ui, uo, uy, has the sound of w or of oo feeble; as in persuade, query, quell, quiet, languid, quote, obloquy.
Ua, an improper diphthong, has the sound—1. Of middle a; as in guard, guardian. 2. Of close a; as in guarantee, piquant. 3. Of obscure e; as in victuals and its compounds or kindred. 4. Of open u; as in mantuamaker.
Ue, an improper diphthong, has the sound—1. Of open u; as in blue, ensue, ague. 2. Of close e; as in guest, guesser. 3. Of close u; as in leaguer. Ue final is sometimes silent; as in league, antique. Ui, an improper diphthong, has the sound—1. Of open i; as in guide, guile. 2. Of close i; as in conduit, circuit. 3. Of open u; as in juice, sluice, suit.
Uo can scarcely be called an improper diphthong, except, perhaps, after q in liquor, liquorice, liquorish, where uor is heard as ur.