This is the 4189th most frequent Polish word.
cytryny
Lemons.
In this sentence, 'cytryny' is used in the accusative plural form, meaning 'lemons', as the direct object of the verb 'kupiłem'.
Kupiłem dwie cytryny na targu.
I bought two lemons at the market.
Here, 'cytryny' is in the genitive singular form, part of the phrase 'tej cytryny' meaning 'of this lemon', used to specify ownership and characterize the taste.
Smak tej cytryny jest naprawdę kwaśny.
The taste of this lemon is really sour.
In this instance, 'cytryny' appears in the genitive singular form again, used to denote association in the phrase 'plasterek cytryny', meaning 'slice of lemon'.