cen·ten·ni·al 
/sɛnˈtɛniəl/ noun
plural cen·ten·ni·als /sɛnˈtɛniəl/ noun [count] US : the 100th anniversary of something (such as an important event)
▪ We're celebrating the museum's centennial [=(Brit) centenary] this summer. [=celebrating the fact that it is 100 years old] ▪ Next year will be the centennial of the town's founding. [=the day/year 100 years after the town was officially begun] — compare bicentennial
▪ We're celebrating the museum's centennial [=(Brit) centenary] this summer. [=celebrating the fact that it is 100 years old] ▪ Next year will be the centennial of the town's founding. [=the day/year 100 years after the town was officially begun] — compare bicentennial
— centennial adjective always used before a noun
▪ a centennial year/celebration
▪ a centennial year/celebration
