This is the 18th most frequent Greek word.
ήταν
"Ήταν" means "was" in English.
In this sentence, 'ήταν' (was) is the past tense of 'είμαι' (to be), indicating a state or condition in the past.
Ένας καλός δάσκαλος ήταν αυτός που με δίδαξε.
A good teacher was the one who taught me.
Here, 'ήταν' describes the past state or characteristic of the subject, the house.
Το σπίτι ήταν μεγάλο και όμορφο.
The house was big and beautiful.
In this example, 'ήταν' is used to reflect the past condition of the weather.