What is the meaning of us?

noun

• A base containing nitrogen that is found in RNA (but not in DNA) and derived from pyrimidine; pairs with adenine.
  • synonyms: uracil, U
• A heavy toxic silvery-white radioactive metallic element; occurs in many isotopes; used for nuclear fuels and nuclear weapons.
  • synonyms: uranium, U, atomic number 92
• The 21st letter of the Roman alphabet.
  • synonyms: U, u
• North American republic containing 50 states - 48 conterminous states in North America plus Alaska in northwest North America and the Hawaiian Islands in the Pacific Ocean; achieved independence in 1776.
  • synonyms: United States, United States of America, America, the States, U. S., USA, U. S. A.