This is the 2351st most frequent Russian word.
неделя
Week.
Here, 'неделя' functions as the subject in the sentence, indicating a specific week referred to.
Эта неделя была очень продуктивной.
This week was very productive.
'Неделя' is used in the accusative case after the quantifying word 'каждую', indicating regularity in time.
Каждую неделю я хожу в библиотеку.
Every week I go to the library.
'Неделя' appears in the prepositional case after 'на', referring to a specific future week.