This is the 2808th most frequent Polish word.
jesiennej
"Jesiennej" means "autumnal" or "of autumn" in English.
Here 'jesiennej' is an adjective in the genitive case modifying the noun 'pogody' (weather) to describe it as autumn-related.
Podczas jesiennej pogody deszcz często pada.
During autumn weather, it often rains.
In this sentence, 'jesiennej' is an adjective in the genitive case describing the noun 'mgły' (fog) as being associated with autumn.
Spacerowaliśmy wśród jesiennej mgły.
We walked amidst the autumn fog.
Here, 'jesiennej' is an adjective in the genitive case modifying the noun 'ziemi' (earth), expressing the characteristic of belonging to the autumn season.