definiens: means the period commencing on First Commercial S ale of the Product in the U.S. by [COMPANY] or its Affiliat e or Sublicensee and expiring upon the expiration o f the fourth Net Sales Calendar Year . means each of ( a ) ( i ) the year in which the First Commercial Sale of the Product is made in the U.S. by [COMPANY] or its Affiliate or Sublicensee, if such First Commer cial Sale is made on or before March 31st of the applicable cale ndar year or ( ii ) the first full calendar year foll owing the date on which the First Commercial Sale of the Product i s made in the U.S. by [COMPANY] or its Affiliate or Sub licensee, if such First Commercial Sale is made after March 31st of the applicable calendar year ( ( i ) or ( ii ), the ), and ( b ) each of the three calendar years immedi ately following the First Net Sales Calendar Year