centenary
Concise Oxford English Dictionary © 2008 Oxford University Press:
centenary /sɛnˈtiːnəri, -ˈtɛn-/
▶noun (pl. centenaries) Brit. the hundredth anniversary of a significant event.
– origin C17: from L. centenarius ‘containing a hundred’, based on L. centum ‘a hundred’.
'centenary' also found in these Oxford entries:

