This is the 8562nd most frequent Dutch word.
honderdjarig
"Centenarian" or "hundred-year-old."
Here, 'honderdjarig' functions as an adjective describing 'bestaan' (existence), indicating a duration of one hundred years.
Het honderdjarig bestaan van de school werd groots gevierd.
The hundred-year anniversary of the school was celebrated grandly.
In this sentence, 'honderdjarig' is used as an adjective qualifying 'boom' (tree), emphasizing its age of one hundred years.
Er was een honderdjarige boom in het park.
There was a hundred-year-old tree in the park.
Here, 'honderdjarig' is used to modify 'traditie' (tradition), imparting the idea of a tradition lasting for one century.