noun / adjective
centennial
sen-TEN-ee-ul/senˈteniəl/
Marking or spanning one hundred years.
They celebrate the hall's centennial beside a cake marked one hundred.

Etymology
Centum supplies the hundred, while the ending modeled on biennial supplies the year-based interval. An adjective meaning lasting or recurring every hundred years became a noun for the hundredth-anniversary celebration.
In context
this is an interesting year for Disney it's their 100th it's a centennial
More examples
- The town holds a centennial parade.
- The museum opens a centennial exhibition.
- Preparations for the college's centennial begin a year early.
Forms
centennial · centennials
Similar words
- centenary
- Another term for a hundredth anniversary, especially outside American English.
- bicentennial
- Marks two hundred years rather than one hundred.