What is the meaning of commencement?

noun

• The time at which something is supposed to begin.
  • usage: "they got an early start"; "she knew from the get-go that he was the man for her"
  • synonyms: beginning, first, outset, get-go, start, kickoff, starting time, showtime, offset
• An academic exercise in which diplomas are conferred.
  • synonyms: commencement exercise, commencement ceremony, graduation, graduation exercise
• The act of starting something.
  • usage: "he was responsible for the beginning of negotiations"
  • synonyms: beginning, start