u u /ˈjuː/

adjective

1. [Informal, British] (chiefly British) of or appropriate to the upper classes especially in language use  ( u [Informal, British] )
   (chiefly British) of or appropriate to the upper classes especially in language use
   

 U

noun

1. The 21st letter of the Roman alphabet  ( U )
   the 21st letter of the Roman alphabet
   
2. A heavy toxic silvery-white radioactive metallic element; occurs in many isotopes; used for nuclear fuels and nuclear weapons  ( atomic number 92 , U , uranium )
   a heavy toxic silvery-white radioactive metallic element; occurs in many isotopes; used for nuclear fuels and nuclear weapons
   
   
3. A base containing nitrogen that is found in RNA (but not in DNA) and derived from pyrimidine; pairs with adenine  ( U , uracil )
   a base containing nitrogen that is found in RNA (but not in DNA) and derived from pyrimidine; pairs with adenine