This is the 14th most frequent Greek word.
στη
The Greek word "στη" means "at the" or "in the" (feminine singular).
The word 'στη' is used here to denote the preposition 'to' combined with the definite article 'τη' for the feminine singular noun 'βιβλιοθήκη' (library).
Πηγαίνω στη βιβλιοθήκη.
I am going to the library.
In this sentence, 'στη' combines the preposition 'σε' (in/on/at) with the definite article 'τη' for the feminine singular noun 'θέση' (place).
Βάζω το βιβλίο στη θέση του.
I put the book in its place.
Here, 'στη' is employed to indicate 'in' and is paired with the definite article 'τη' for 'νότια' modifying the feminine noun 'Ελλάδα' (Greece).