noun (n)

• the time at which something is supposed to begin(noun.time)

  Synonym:
  beginning, first, get-go, kickoff, offset, outset, showtime, start, starting time
  Antonym:
  end, ending
  

  source: wordnet30
• an academic exercise in which diplomas are conferred(noun.event)

  Synonym:
  commencement ceremony, commencement exercise, graduation, graduation exercise
  

  source: wordnet30
• the act of starting something(noun.act)

  Synonym:
  beginning, start
  Antonym:
  finish, finishing
  

  source: wordnet30
• The first existence of anything; act or fact of commencing; rise; origin; beginning; start.(noun)

  source: webster1913