If your parents are celebrating their centennial wedding anniversary, make sure you throw them a really big party. Centennial is a word to describe something that has lasted for 100 years — so your parents have been married an unusually long time!
When you notice the cent- bit in the word centennial you probably think of words like century (100 years) and cent (100 pennies that make up a dollar), and that tips you off that centennial has something to do with the number 100. What these words all share in common is an origin in the Latin word centum, meaning 100. In the case of the adjective centennial, the addition of -ennial gives the word its sense of describing a one hundred year anniversary.