This is the 159th most frequent Greek word.
στις
"Στις" means "at" or "on" and is used to indicate a specific time or place.
Here, 'στις' is used to indicate a specific time, showing an adverbal function related to the preposition.
Βρίσκεται στις δώδεκα η ώρα.
It is located at twelve o'clock.
In this context, 'στις' is used to denote location with a definite article, referring to a plural feminine noun (όχθες).
Μένουμε στις όχθες του ποταμού.
We live by the banks of the river.
In this sentence, 'στις' is a preposition used in conjunction with the article to denote direction or destination, referring to a plural feminine noun (αγορές).