What is the meaning of institution?

noun

• An organization founded and united for a specific purpose.
  • synonyms: establishment
• An establishment consisting of a building or complex of buildings where an organization for the promotion of some cause is situated.
• A custom that for a long time has been an important feature of some group or society.
  • usage: "the institution of marriage"; "the institution of slavery"; "he had become an institution in the theater"
• The act of starting something for the first time; introducing something new.
  • usage: "she looked forward to her initiation as an adult"; "the foundation of a new scientific society"
  • synonyms: initiation, founding, foundation, origination, creation, innovation, introduction, instauration
• A hospital for mentally incompetent or unbalanced person.
  • synonyms: mental hospital, psychiatric hospital, mental institution, mental home, insane asylum, asylum