1. The 21st letter of the Roman alphabet
   - U

1. (chiefly British) of or appropriate to the upper classes especially in language use
   "Her u accent marked her as coming from a privileged background"

1. A heavy toxic silvery-white radioactive metallic element; occurs in many isotopes; used for nuclear fuels and nuclear weapons
   - uranium, atomic number 92
    
2. A base containing nitrogen that is found in RNA (but not in DNA) and derived from pyrimidine; pairs with adenine
   "U replaces thymine in RNA molecules";
   - uracil

Derived forms: Us

See also: posh [Brit, informal], upper-class

Type of: alphabetic character, base, letter, letter of the alphabet, metal, metallic element, nucleotide

Part of: Latin alphabet, pitchblende, ribonucleic acid, RNA, Roman alphabet, uraninite

Encyclopedia: U, Federated States of Micronesia