U, n.
the 21st letter of the Roman alphabet
<noun.communication>
U u
semantic pointers
member holonym
hypernym
a heavy toxic silvery-white radioactive metallic element; occurs in many isotopes; used for nuclear fuels and nuclear weapons
<noun.substance>
U atomic number 92 uranium
semantic pointers
hypernym
substance holonym
hyponym
a base containing nitrogen that is found in RNA (but not in DNA) and derived from pyrimidine; pairs with adenine
<noun.substance>
U uracil