This is the 423rd most frequent Lithuanian word.
mėnesius
The Lithuanian word "mėnesius" translates to "months" (accusative plural) in English.
In this sentence, 'mėnesius' is the accusative plural form of 'mėnuo' (month) used to indicate the duration of time.
Aš studijavau užsienyje tris mėnesius.
I studied abroad for three months.
Here, 'mėnesiams' is the dative case of 'mėnesis' (month) used to denote the point in time after a certain period.
Praėjus šešiems mėnesiams, jis pradėjo naują darbą.
After six months, he started a new job.
In this example, 'mėnesius' again appears in the accusative plural form of 'mėnuo,' used to specify an entire period of time.