O | Webster's Dictionary (1865)

O

the fifteenth letter, and the fourth vowel, in the English alphabet, has several different sounds, the principal of which are, the long sound, heard in tone, groan, old; the short sound, heard in lot, lodge, rod; a sound like short u, as in done, son, flood; a sound like the German or Italian long u, or the French ou, as in move, do, booty; a similar but shorter sound, as in wolf, book, foot; and a sound like broad a, as in form, mortal. See Principles of Pronunciation, §§ 19-25, 50, 51. In Irish family names, O is equivalent to son of, and denotes progeny, or is a character of dignity; as, O’Neil; O’Carrol. 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.

O, interj.

interjection

An exclamation used in calling or directly addressing a person or personified object;—used also as an impassioned exclamation expressing pain, grief, surprise, desire, and the like.

For ever, O Lord, thy word is settled in heaven. Ps. cix. 89.

O, how love I thy law! it is my meditation all the day. Ps. cxix. 97.

O fairest of creation, last and best Of all God's works. Milton.

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 should be used in mere 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. This distinction, however, is nearly or totally disregarded by most writers, even the best, the two forms being generally used quite indiscriminately. The form O is the one most commonly employed for both uses by modern writers. “O for a kindling touch from that pure flame!” Wordsworth. “O, what a rapturous cry!” “O! Eldon, in whatever sphere thou shine.” “Strike, oh Muse, in a measure bold.” Macaulay. “O, what a fair and ministering angel!” “O sweet angel.” Longfellow.

For you the public prayer is made; Oh! join the public prayer! For you the secret tear is shed; O, shed yourselves a tear. Cowper.

O sir, oh prince, I have no country; none. Tennyson.

O, a.

adjective

a. An abbreviation for one. [Obs.]

Abraham seith That he seigh hooly the Trinite, Thre persones in parcelles Departable fro o other And alle thre but o God. Piers Plowman.

O, n.

noun

n. Something shaped like the letter O; a circle or oval.

May we cram Within this wooden O [the Globe Theater] the very casques That did affright the air at Agincourt? Shak.