This is the 1159th most frequent Polish word.
tygodnie
"Weeks"
Here, 'tygodnie' is used in plural to indicate a period of time, 'two weeks'.
Przez ostatnie dwa tygodnie pracowałem nad projektem.
I have been working on the project for the last two weeks.
In this case, 'tygodnie' refers to an indefinite number of weeks.
W ciągu kilku tygodni powinienem skończyć książkę.
I should finish the book within a few weeks.
Here, 'tygodnie' indicates forthcoming, consecutive weeks.