What is the meaning of happen?

verb

• Come to pass.
  • usage: "What is happening"; "The meeting took place off without an incidence"; "Nothing occurred that seemed important"
  • synonyms: hap, go on, pass off, occur, pass, fall out, come about, take place
• Happen, occur, or be the case in the course of events or by chance."It happens that today is my birthday"; "These things befell" (Santayana)
  • synonyms: befall, bechance
• Chance to be or do something, without intention or causation.
  • usage: "I happen to have just what you need"
• Come into being; become reality.
  • usage: "Her dream really materialized"
  • synonyms: materialize, materialise
• Come upon, as if by accident; meet with.
  • usage: "We find this idea in Plato"; "I happened upon the most wonderful bakery not very far from here"; "She chanced upon an interesting book in the bookstore the other day"
  • synonyms: find, chance, bump, encounter