This is the 42nd most frequent Hungarian word.
óta
"Óta" means "since" in English.
Here, 'óta' is used to relate to a specific event ('elutazott' = 'he left') as the starting point of a time period.
Nem láttam őt azóta, hogy elutazott.
I haven't seen him since he left.
This sentence shows 'óta' in relation to an abstract time period or event ('Tanulmányaink' = 'our studies') designating the starting point.
Tanulmányaink óta tartjuk a kapcsolatot.
We have kept in touch since our studies.
In this sentence, 'óta' is used to indicate a point in time from which the period starts ('építése óta' = 'since the construction').