| O |
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noun
- The fifteenth letter of the Appendix:Roman script, English alphabet, preceded by N and followed by P.
- A blood type that has no antigens and may only receive type O blood and nothing else, but may donate to all.
abbreviation
- (cricket) The number of overs bowled.
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| occlude |
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verb (occlud, ing)
- To obstruct, cover, or otherwise block an opening.
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| octad |
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noun
- a group of eight things
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| octane |
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noun
- (chemistry) Any of the eighteen isomeric aliphatic hydrocarbons (C8H18) found in petroleum, especially an iso-octane 2,2,4 trimethyl-pentane; they are used as fuels and solvents
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| octane number |
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noun
- a measure of the antiknock properties of an automobile fuel; isooctane having an octane number of 100, a fuel with the same antiknock properties as a mixture of 90% isooctane and 10% heptane having an octane number of 90
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| octavalent |
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adjective - (chemistry) having a valence of 8
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| oil |
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noun
- liquid, Liquid fat.
- petroleum, Petroleum-based liquid used as fuel or lubricant.
verb
- (transitive) to lubricate with oil
- (transitive) to grease with oil for cooking
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| oil of wintergreen |
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noun
- The aromatic oil obtained from the berries of the wintergreen plant; mostly methyl salicylate; used medicinally and in perfumes
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| oily |
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adjective (oilier, oiliest)
- Relating to oil.
- Smeared with or containing oil.
- (figurative) Excessively friendly or polite so as to sound insincere.
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| oleate |
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noun - (chemistry) any salt or ester of oleic acid
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| olefin |
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noun
- (organic chemistry) Any of a class of unsaturated open-chain hydrocarbons such as ethylene; an alkene with only one carbon-carbon double bond.
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| oleic acid |
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noun
- an unsaturated fatty acid found in olive oil and very many other vegetable and animal oils and fats; it is used for making soap, cosmetics etc.
- (chemistry) cis-9-octadecenoic acid
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| oleum |
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noun
- (inorganic compound) A solution of sulfur trioxide in sulfuric acid.
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| oligomer |
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noun - (chemistry) a compound intermediate between a monomer and a polymer, normally having a specified number of units between about five and a hundred.
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| oligosaccharide |
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noun - (chemistry) a polysaccharide of low molecular weight, being a polymer of between three and seven monosaccharide units
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| optical activity |
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noun (wikipedia, optical rotation)
- (chemistry) a property caused by asymmetrical molecular or crystal structure that enables a compound or crystal to rotate the plane of incident polarized light
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| optical isomer |
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noun - (chemistry) either one of a number of compounds that exhibit optical isomerism
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| orcein |
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noun - (chemistry) a dye, related to litmus, that is extracted from the lichen Rocella tinctoria; used as a microscopic stain and as a food colouring
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| orchil |
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noun
- Any of several lichens, especially those of the genera Roccella and Lecanora.
- The dye, orcein, extracted from them.
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| organic |
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adjective
- (biology) pertaining to, derived from, like, of the nature of, an organ of the body
- (chemistry) relating to the compounds of carbon, relating to natural products
- of food or food products, grown in an environment free from artificial agro-chemicals, and possibly certified organic by a regulatory body.
- (sociology) a form of social solidarity theorized by Emile Durkheim that is characterized by voluntary engagements in complex interdepencies for mutual benefit (such as business agreements), rather than mechanical solidarity, which depends on ascribed relations between people (as in a family or tribe).
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| organic chemistry |
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noun
- (chemistry) The chemistry of carbon-containing compounds, especially those that occur naturally in living organisms.
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| organometallic |
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adjective - (chemistry) of, or relating to organic compounds having a metal atom directly bonded to a carbon atom
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| organosilicon |
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adjective - (chemistry) describing any of a series of derivatives of silicon that have at least one alkyl or aryl group, especially one containing at least one carbon-silicon bond
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| OS |
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initialism
- Ordnance Survey
- operating system
- oculus sinister () - left eye
- outsize
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| osmium |
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noun
- a heavy metallic chemical element (symbol Os) with an atomic number of 76.
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| osmium tetroxide |
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noun - (chemistry) an oxide of the metal osmium, OsO?4; it is very poisonous, has a pungent smell and can cause blindness; it is a powerful oxidizing agent, and is used to stain biological materials
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| osmotic pressure |
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noun - (physics) The hydrostatic pressure exerted by a solution across a semipermeable membrane from a pure solvent; the pressure needed to counteract osmosis
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| outgas |
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verb
- To release gaseous substances into the air, especially of a polymer material as it is aged or heated.
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| oxalic |
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adjective - Pertaining to, derived from, or contained in, sorrel, or oxalis; specifically, an acid found in, and characteristic of, oxalis.
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| oxalic acid |
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noun
- (organic compound) A colourless, crystalline poisonous dicarboxylic acid, (COOH)2, found in rhubarb, spinach and other plants, often as crystals of the calcium salt.
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| oxidant |
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noun
- an oxidizing agent
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| oxidate |
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verb to oxidate
- (obsolete),(chemistry) to oxidize
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| oxidation |
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noun
- The combination of a substance with oxygen.
- (chemistry) A reaction in which the atoms of an element lose electrons and the valence of the element increases.
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| oxidation state |
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noun
- (chemistry) the state of an atom having a particular oxidation number
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| oxide |
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noun
- (chemistry) A binary chemical compound of oxygen with another chemical element.
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| oxidimetry |
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noun - (chemistry) any form of volumetric analysis using an oxidizing agent such as potassium permanganate
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| oxidize |
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verb (oxidizes, oxidizing, oxidized)
- (chemistry, transitive) To combine with oxygen or otherwise make an oxide.
- (chemistry) To increase the valence (or the positive charge) of an element by removing electrons.
- To coat something with an oxide.
- (intransitive) To become oxidized.
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| oxidizer |
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noun - (chemistry) An oxidizing agent, especially one used to oxidize the fuel of a rocket or a fuel cell
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| oxidizing agent |
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noun - (chemistry) any substance that oxidizes, or receives electrons from, another; in so doing, it becomes reduced
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| oxime |
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noun
- (organic chemistry) Any of a class of organic compounds, of general formula RR'C=NOH, derived from the condensation of an aldehyde (R' = H) or ketone with hydroxylamine.
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| oxy- |
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prefix - Concerning oxygen
- Sharp, keen, acute, pungent, acid
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| oxyacetylene |
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noun - A mixture of oxygen and acetylene; burns at a high temperature and is used for cutting and welding metals.
adjective
- Using this mixture e.g. an oxyacetylene torch
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| oxyacid |
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noun - (chemistry) An acid containing oxygen, as opposed to a hydracid.
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| oxychloride |
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noun - (chemistry) A ternary compound of oxygen and chlorine.
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| oxygen |
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noun
- A chemical element (symbol O) with an atomic number of 8 and relative atomic mass of 15.9994.
- An atom of this element.
- Molecular oxygen (O2), a colorless, odorless gas at room temperature.
- (medicine) A mixture of oxygen and other gases, administered to a patient to help him or her to breathe.
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| oxygenize |
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verb (oxygenizes, oxygenizing, oxygenized)
- To oxidize.
- To oxygenate.
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| oxyhydrogen |
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adjective
- of, or using a mixture of hydrogen and oxygen
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| ozonide |
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noun - (chemistry) the univalent anion, O3-, derived from ozone
- (chemistry) any dark red salt of this anion and a metal
- (chemistry) any of a number of explosive organic compounds containing a -O-O-O- group
- (chemistry) any of a class of heterocycles, containing two carbon atoms (in positions 3 and 5) and three oxygen atoms (in positions 1, 2 and 4) produced by the reaction of ozone with a carbon to carbon double bond; the 1,2,4-trioxolanes
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