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noun
- The twenty-first letter of the Appendix:Roman script, English alphabet.
adjective
- (context, mostly, British) Characteristic of the upper classes, particularly in use of language.
abbreviation
- (British film certificate) Universal - suitable for all ages
- Under
- University
- Up, Upper
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| unbound |
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verb
- past tense of to unbind
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| univalent |
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adjective
- (chemistry) Having a valence of 1, or having only one valence.
- (genetics) Of, or relating to a chromosome that is not paired with its homologous chromosome during synapsis.
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| unsaturated |
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adjective
- (context, chemistry, of a solution) Not saturated; capable of dissolving more of a solute at the same temperature.
- (chemistry) Of a compound containing atoms sharing more than one valence bond, especially of an organic compound having one or more double bonds or triple bonds between carbon atoms.
- (context, of a colour) Not chromatically pure; diluted.
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| unstable |
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adjective
- Having a strong tendency to change
- fluctuate, Fluctuating; not constant
- fickle
- unpredictable
- (chemistry) Readily decompose, decompasable
- (physics) radioactive, Radioactive, especially with a short half-life
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| Urania |
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proper noun
- (Greek mythology) The Muse of astronomy.
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| uranic |
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adjective - (chemistry) Containing uranium in higher valences than uranous compounds.
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| uranium hexafluoride |
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noun - (chemistry) a binary compound of uranium and fluorine, UF6; it is a grey solid, or heavy gas, and is used in the uranium enrichment process to produce fuel for nuclear reactors or nuclear weapons
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| uranous |
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adjective - (chemistry) Containing uranium in higher valences than uranic compounds.
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| uranyl |
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noun - (chemistry) The divalent radical UO22+, conveniently regarded as a residue of many uranium compounds.
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| urate |
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noun - (chemistry) any salt of uric acid; the deposition of urate crystals in the joints leads to gout
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| urea |
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noun
- (biochemistry) A water-soluble organic compound, CO(NH2)2, formed by the metabolism of proteins and excreted in the urine.
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| ureide |
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noun - (chemistry) any compound, of general formula R-CO-NH-CO-NH2 or R-CO-NH-CO-NH-CO-R', formally derived by the acylation of urea
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| urethane |
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noun
- (organic compound, uncountable) A white crystalline organic compound, ethyl-carbamate, NH2COOC2H5, used in the synthesis of other organic compounds.
- (organic chemistry, countable) Any compound of having this general structure.
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| uric acid |
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noun - (chemistry) a bicyclic heterocyclic phenolic compound, formed in the body by the metabolism of protein and excreted in the urine (or in avian faeces)
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