U

Definitions of U

1. noun

   the 21st letter of the Roman alphabet
   synonyms: u

   type of:

   alphabetic character, letter, letter of the alphabet

   the conventional characters of the alphabet used to represent speech
2. noun

   a heavy, silvery-white, highly radioactive metallic element used for nuclear fuel and weapons
   synonyms: atomic number 92, uranium

   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

   type of:

   base, nucleotide

   a phosphoric ester of a nucleoside; the basic structural unit of nucleic acids (DNA or RNA)