The fifteenth letter and fourth vowel in our alphabet.It thus appears that the belief, not uncommonly held, that O represents, and is imitated from, the rounded position of the lips in its utterance, is a delusion. The historical value of the letter (as already noticed) is that of our o, in note, etc., whether of both long and short quantities, as in Latin and the earliest Greek, or of short only, as in Greek after the addition to that alphabet of a special sign for long o (namely omega, Ω, ω). This vowel-sound, the name-sound of o, is found in English usage only with long quantity in accented syllables. There is no closely corresponding short vowel in standard English, but only in dialectal pronunciation, as in the New England utterance of certain words (much varying in number in different individuals): for example, home, whole, none. What we call “short o” (in not, on, etc.) is a sound of altogether different quality, very near to a true short ä (that is, a short utterance corresponding to the a of arm, father), but verging slightly toward the “broad” a (â) or o (ô) of laud, lord. “Short o” has a marked tendency to take on a “broader” sound, especially before r, and especially in America: hence the use, in the respellings of this work, of ô, which varies in different mouths from the full sound of â to that of ŏ. After these three values of the character, the next most common one is that of the oo-sonnd, the original and proper sound of u (represented in this work by ö), as in move, with the nearly corresponding short sound (marked u) in a few words, as wolf, woman. All these vowel-sounds partake of what is usually called a “labial” or a “rounded” character: that is to say, there is involved in their utterance a rounding and closing movement of the lips (and, it is held, of the whole mouth-cavity), in different degrees — least of all in ŏ, more and more in â, ō, u, ö; in the last, carried to its extreme, no closer rounding and approximation being possible. The labial action helps to give the vowel-sounds in question their fully distinctive character; but it can be more or less slighted without leaving them unrecognizable, and, in the generally indifferent habit of English pronunciation, is in a degree neglected, even in accented syllables, and yet more in unaccented. Our “long ō,” it should be added, regularly ends with a vanishing sound of oo (ö), as our ā with one of ē. O also has in many words the value of the “neutral” vowels of hut, hurt: for example, in son, come, love, work. O is further a member of several very common and important digraphs: thus, oo, the most marked representative of the ö-sound (in moon, rood, etc.), but also pronounced as u (book, look, etc.) and ŭ (blood, etc.); ou (in certain situations ow), oftenest representing a real diphthong (in out, sound, now, etc.), but also a variety of other sounds (as in through, could, ought, rough); oi (in certain situations oy), standing for a real diphthongal sound of which the first element is the “broad” o- or a-sound (for example, point, boy); oa (load, etc.), having the “long” o-sound; others, as eo (variously pronounced, as in people, yeoman, jeopard), oe (in foe, does, etc.), are comparatively rare.As a medieval Roman numeral, 11.As a symbol: In medieval musical notation, the sign of the tempus perfectum — that is, of triple rhythm. See mensurable music, under mensurable.In modern musical notation, a null (which see)In chem., the symbol of oxygen.In logic, the symbol of the particular negative proposition. See A, 2 .An abbreviation: Of old: as, in O. H. G., Old High German; O. T., Old Testament.Of the Middle Latin octavius, a pint.[lowercase] In a ship's log-book, of overcast.Pl. o's, oes (ōz). Anything circular or approximately so, as resembling the shape of the letter o, as a spangle, the circle of a theater, the earth, etc.An arithmetical cipher; zero: so called from its form.A common interjection expressing surprise, pain, gladness, appeal, entreaty, invocation, lament, etc., according to the manner of utterance and the circumstances of the case.n. An exclamation or lamentation.n. Same as ho.An abbreviated form of on. Commonly written o'.Same as one.Same as a, the indefinite article.An abbreviated form of of, now commonly written o'.A prefix common in Irish surnames, equivalent to Mac-in Gaelic and Irish surnames (see Mac), meaning ‘son,’ as in O'Brien, O'Connor, O'Donnell, O'Sullivan, son of Brien, Connor, Donnell, etc.The usual “connecting vowel,” properly the stem-vowel of the first element, of compound words taken or formed from the Greek, as in acr-o-lith, chrys-o-prase, mon-o-tone, prot-o-martyr, etc.An abbreviationin electricity, of ohm;of Ohio;of only;of opening of the circuit;in psychology, of observer.