U

名词 u:

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

形容词 u:

1. (chiefly British) of or appropriate to the upper classes especially in language use