What is the meaning of formation?

noun

• An arrangement of people or things acting as a unit.
  • usage: "a defensive formation"; "a formation of planes"
• The act of fabricating something in a particular shape.
  • synonyms: shaping
• The act of forming or establishing something.
  • usage: "the constitution of a PTA group last year"; "it was the establishment of his reputation"; "he still remembers the organization of the club"
  • synonyms: constitution, establishment, organization, organisation
• Geology) the geological features of the earth.
  • synonyms: geological formation
• A particular spatial arrangement.
• Natural process that causes something to form.
  • usage: "the formation of gas in the intestine"; "the formation of crystals"; "the formation of pseudopods"
• Creation by mental activity.
  • usage: "the formation of sentences"; "the formation of memories"