This is the 675th most frequent Czech word.
letošní
This year's.
The word 'letošní' describes the current year's winter, hence specifying it temporally.
Letošní zima byla velmi teplá.
This year's winter was very warm.
'Letošní' is applied attributively to 'úroda', specifying the harvest of the current year.
Letošní úroda brambor byla bohatá.
This year's potato harvest was abundant.
The term 'letošním' is used in the locative case to indicate that the festival is held in the current year.