com·mence·ment
 /kəˈmɛnsmənt/  noun  ,  pl   -ments
   formal  
  1 [  noncount  ] : the time when something begins : beginning
  — usually + of
   They awaited the commencement of the trial.
   It's the first attempt at peace since the commencement [=start] of hostilities.
  2 US : a ceremony during which degrees or diplomas are given to students who have graduated from a school or college
   [  noncount  ] the week before commencement [=graduation]
   [  count  ] A poet will speak at the commencement.
    — often used before another noun
    a commencement speech/address/ceremony
    commencement exercises