This is the 6120th most frequent Russian word.
столетия
"Столетия" means "centuries" in English.
In this sentence, 'столетия' is used as a time measure in the context of centuries ago.
Столетия назад люди жили иначе.
Centuries ago, people lived differently.
Here, 'столетия' denotes the duration over which a tradition has existed.
Эта традиция продолжается уже несколько столетий.
This tradition has been ongoing for several centuries.
In this context, 'столетия' refers to periods of long times into the future that could be affected.