|o or O (əʊ)|
|—n , pl o's, O's, Os|
|1.||the 15th letter and fourth vowel of the modern English alphabet|
|2.||any of several speech sounds represented by this letter, in English as in code, pot, cow, move, or form|
|3.||another name for nought|
|O or O|
|2.||See universal donor a human blood type of the ABO group|
|3.||logic A E Compare I a particular negative categorial proposition, such as some men are not married: often symbolized as SoP|
|4.||slang (Austral) offence|
|[(for sense 3) from Latin (neg)o I deny]|
|1.||a variant spelling of oh|
|2.||an exclamation introducing an invocation, entreaty, wish, etc: O God!; O for the wings of a dove!|
|—n , pl ossa|
|anatomy the technical name for bone|
|[C16: from Latin: bone; compare Greek osteon]|
|—the chemical symbol for|
|2.||Old Style (method of reckoning dates)|
|4.||(in Britain) Ordnance Survey|
|6.||Old Saxon (language)|
|o.s., OS or O/S|
|1.||out of stock|
|OS, OS or O/S|
|O/S, OS or O/S|
The Greek letter omicron. Entries beginning with this character are alphabetized under omicron.
The symbol for the element oxygen.
os 1 (ŏs)
n. pl. o·ra (ôr'ə)
An opening into a hollow organ or canal.
The oral cavity; mouth.
os 2 (ŏs)
n. pl. os·sa (ŏs'ə)
The symbol for the element osmium.
Latin oculus sinister (left eye)
The symbol for oxygen.
The symbol for osmium.
|osmium (ŏz'mē-əm) Pronunciation Key
A hard, brittle, bluish-white metallic element that is the densest naturally occurring element. It is used to make very hard alloys for fountain pen points, electrical contacts, and instrument pivots. Atomic number 76; atomic weight 190.2; melting point 3,000°C; boiling point 5,000°C; specific gravity 22.57; valence 2, 3, 4, 8. See Periodic Table.
(Os), chemical element, one of the platinum metals of Group VIIIb of the periodic table and the densest naturally occurring element. A gray-white metal, osmium is very hard, brittle, and difficult to work, even at high temperatures. Of the platinum metals it has the highest melting point, so fusing and casting are difficult. Osmium wires were used for filaments of early incandescent lamps before the introduction of tungsten. It has been used chiefly as a hardener in alloys of the platinum metals, though ruthenium has generally replaced it. A hard alloy of osmium and iridium has been used for tips of fountain pens and phonograph needles, and osmium tetroxide is used in certain organic syntheses.
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