This is the 517th most frequent Lithuanian word.
mėnesio
"Of the month."
In this sentence, 'mėnesio' is used as a possessive form of 'mėnuo' (month), describing the time frame associated.
Per šį mėnesio laikotarpį daug kas pasikeitė.
During this month-long period, many things changed.
Here, 'mėnesio' is possessive, denoting that the report pertains to the end of a month.
Tai yra mėnesio pabaigos ataskaita.
This is the month's end report.
In this usage, 'mėnesio' indicates the possessive form, referring to the particular point in time linked to a month.