This is the 249th most frequent Russian word.
недели
The Russian word "недели" means "weeks" (genitive singular or nominative/accusative plural of "неделя").
The word "недели" is used here in the genitive singular form to indicate a specific within a week ('of this week').
На этой неделе будет встреча.
There will be a meeting this week.
The word "недели" appears here in the genitive plural form, used after "несколько" (several) to indicate duration.
Я отсутствовал несколько недель.
I was absent for several weeks.
Here, "недели" is used in the nominative plural form as the subject of the sentence, referring to several weeks during spring.