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U

Definitions of U
  1. noun
    the 21st letter of the Roman alphabet
    synonyms: u
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    type of:
    alphabetic character, letter, letter of the alphabet
    the conventional characters of the alphabet used to represent speech
  2. noun
    a heavy toxic silvery-white radioactive metallic element; occurs in many isotopes; used for nuclear fuels and nuclear weapons
    synonyms: atomic number 92, uranium
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    types:
    uranium 235
    a uranium isotope with mass number 235; capable of sustaining chain reactions
    uranium 238
    the commonest isotope of uranium; it is not fissionable but when irradiated with neutrons it produces fissionable plutonium 239
    type of:
    metal, metallic element
    any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc.
  3. noun
    a base containing nitrogen that is found in RNA (but not in DNA) and derived from pyrimidine; pairs with adenine
    synonyms: uracil
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    type of:
    base, nucleotide
    a phosphoric ester of a nucleoside; the basic structural unit of nucleic acids (DNA or RNA)
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