1. O, the fifteenth letter of the English alphabet, derives its form, value, and name from the Greek O, through the Latin. The letter came into the Greek from the Phœnician, which possibly derived it ultimately from the Egyptian. Etymologically, the letter o is most closely related to a, e, and u; as in E. bone, AS. bān; E. stone, AS. stān; E. broke, AS. brecan to break; E. bore, AS. beran to bear; E. dove, AS. dūfe; E. toft, tuft; tone, tune; number, F. nombre. [ 1913 Webster ]

The letter o has several vowel sounds, the principal of which are its long sound, as in bone, its short sound, as in nod, and the sounds heard in the words orb, son, do (feod), and wolf (book). In connection with the other vowels it forms several digraphs and diphthongs. See Guide to Pronunciation, §§ 107-129. [ 1913 Webster ]

2. Among the ancients, O was a mark of triple time, from the notion that the ternary, or number 3, is the most perfect of numbers, and properly expressed by a circle, the most perfect figure. [ 1913 Webster ]

O was also anciently used to represent 11: with a dash over it (Ō), 11, 000. [ 1913 Webster ]

n.; pl. O's or Oes 1. The letter O, or its sound. “Mouthing out his hollow oes and aes.” Tennyson. [ 1913 Webster ]

2. Something shaped like the letter O; a circle or oval. “This wooden O [ Globe Theater ]”. Shak. [ 1913 Webster ]

3. A cipher; zero. [ R. ] [ 1913 Webster ]

Thou art an O without a figure. Shak. [ 1913 Webster ]

a. [ See One. ] One. [ Obs. ] Chaucer. “Alle thre but o God.” Piers Plowman. [ 1913 Webster ]

interj. An exclamation used in calling or directly addressing a person or personified object; also, as an emotional or impassioned exclamation expressing pain, grief, surprise, desire, fear, etc. [ 1913 Webster ]

For ever, O Lord, thy word is settled in heaven. Ps. cxix. 89. [ 1913 Webster ]

O how love I thy law ! it is my meditation all the day. Ps. cxix. 97. [ 1913 Webster ]

☞ O is frequently followed by an ellipsis and that, an in expressing a wish: “O [ I wish ] that Ishmael might live before thee!” Gen. xvii. 18; or in expressions of surprise, indignation, or regret: “O [ it is sad ] that such eyes should e'er meet other object!” Sheridan Knowles. [ 1913 Webster ]

☞ A distinction between the use of O and oh is insisted upon by some, namely, that O should be used only in direct address to a person or personified object, and should never be followed by the exclamation point, while Oh (or oh) should be used in exclamations where no direct appeal or address to an object is made, and may be followed by the exclamation point or not, according to the nature or construction of the sentence. Some insist that oh should be used only as an interjection expressing strong feeling. The form O, however, is, it seems, the one most commonly employed for both uses by modern writers and correctors for the press. “O, I am slain!” Shak. “O what a fair and ministering angel!” “O sweet angel !” Longfellow. [ 1913 Webster ]

O for a kindling touch from that pure flame! Wordsworth. [ 1913 Webster ]

But she is in her grave, -- and oh
The difference to me! Wordsworth. [ 1913 Webster ]

Oh for a lodge in some vast wilderness! Cowper. [ 1913 Webster ]

We should distinguish between the sign of the vocative and the emotional interjection, writing O for the former, and oh for the latter. Earle. [ 1913 Webster ]

O dear, and
O dear me! [ corrupted fr. F. O Dieu! or It. O Dio! O God! O Dio mio! O my God! Wyman. ], exclamations expressive of various emotions, but usually promoted by surprise, consternation, grief, pain, etc. [ 1913 Webster ]

. [ Ir. o a descendant. ] A prefix to Irish family names, which signifies grandson or descendant of, and is a character of dignity; as, O'Neil, O'Carrol. [ 1913 Webster ]

prep. A shortened form of of or on. “At the turning o' the tide.” Shak. [ 1913 Webster ]

n. See Woad. [ Obs. ] Coles. [ 1913 Webster ]

n. [ See Auf. ] 1. Originally, an elf's child; a changeling left by fairies or goblins; hence, a deformed or foolish child; a simpleton; an idiot. [ 1913 Webster ]

2. A clumsy or awkward person.
Syn. -- klutz, clod, lummox, stumblebum. [ PJC ]

a. Like an oaf; simple or clumsy. -- Oaf"ish*ness, n. [1913 Webster]

n. [ OE. oke, ok, ak, AS. āc; akin to D. eik, G. eiche, OHG. eih, Icel. eik, Sw. ek, Dan. eeg. ] [ 1913 Webster ]

1. (Bot.) Any tree or shrub of the genus Quercus. The oaks have alternate leaves, often variously lobed, and staminate flowers in catkins. The fruit is a smooth nut, called an acorn, which is more or less inclosed in a scaly involucre called the cup or cupule. There are now recognized about three hundred species, of which nearly fifty occur in the United States, the rest in Europe, Asia, and the other parts of North America, a very few barely reaching the northern parts of South America and Africa. Many of the oaks form forest trees of grand proportions and live many centuries. The wood is usually hard and tough, and provided with conspicuous medullary rays, forming the silver grain. [ 1913 Webster ]

2. The strong wood or timber of the oak. [ 1913 Webster ]

☞ Among the true oaks in America are:
Barren oak, or
Black-jack, Quercus nigra. --
Basket oak, Quercus Michauxii. --
Black oak, Quercus tinctoria; -- called also yellow oak or quercitron oak. --
Bur oak (see under Bur.), Quercus macrocarpa; -- called also over-cup or mossy-cup oak. --
Chestnut oak, Quercus Prinus and Quercus densiflora. --
Chinquapin oak (see under Chinquapin), Quercus prinoides. --
Coast live oak, Quercus agrifolia, of California; -- also called enceno. --
Live oak (see under Live), Quercus virens, the best of all for shipbuilding; also, Quercus Chrysolepis, of California. --
Pin oak. Same as Swamp oak. --
Post oak, Quercus obtusifolia. --
Red oak, Quercus rubra. --
Scarlet oak, Quercus coccinea. --
Scrub oak, Quercus ilicifolia, Quercus undulata, etc. --
Shingle oak, Quercus imbricaria. --
Spanish oak, Quercus falcata. --
Swamp Spanish oak, or
Pin oak, Quercus palustris. --
Swamp white oak, Quercus bicolor. --
Water oak, Quercus aquatica. --
Water white oak, Quercus lyrata. --
Willow oak, Quercus Phellos. [ 1913 Webster ] Among the true oaks in Europe are:
Bitter oak, or
Turkey oak, Quercus Cerris (see Cerris). --
Cork oak, Quercus Suber. --
English white oak, Quercus Robur. --
Evergreen oak,
Holly oak, or
Holm oak, Quercus Ilex. --
Kermes oak, Quercus coccifera. --
Nutgall oak, Quercus infectoria. [ 1913 Webster ]

☞ Among plants called oak, but not of the genus Quercus, are:
African oak, a valuable timber tree (Oldfieldia Africana). --
Australian oak or
She oak, any tree of the genus Casuarina (see Casuarina). --
Indian oak, the teak tree (see Teak). --
Jerusalem oak. See under Jerusalem. --
New Zealand oak, a sapindaceous tree (Alectryon excelsum). --
Poison oak, a shrub once not distinguished from poison ivy, but now restricted to Rhus toxicodendron or Rhus diversiloba. --
Silky oak or
Silk-bark oak, an Australian tree (Grevillea robusta). [ 1913 Webster ]

Green oak, oak wood colored green by the growth of the mycelium of certain fungi. --
Oak apple, a large, smooth, round gall produced on the leaves of the American red oak by a gallfly (Cynips confluens). It is green and pulpy when young. --
Oak beauty (Zool.), a British geometrid moth (Biston prodromaria) whose larva feeds on the oak. --
Oak gall, a gall found on the oak. See 2d Gall. --
Oak leather (Bot.), the mycelium of a fungus which forms leatherlike patches in the fissures of oak wood. --
Oak pruner. (Zool.) See Pruner, the insect. --
Oak spangle, a kind of gall produced on the oak by the insect Diplolepis lenticularis. --
Oak wart, a wartlike gall on the twigs of an oak. --
The Oaks, one of the three great annual English horse races (the Derby and St. Leger being the others). It was instituted in 1779 by the Earl of Derby, and so called from his estate. --
To sport one's oak, to be “not at home to visitors, ” signified by closing the outer (oaken) door of one's rooms. [ Cant, Eng. Univ. ] [ 1913 Webster ]