This is the 10223rd most frequent Polish word.
bułka
A small bread roll.
In this sentence, 'bułkę' refers to a type of bread roll and is in the accusative case as it is the object of the verb 'kupiłem' (I bought).
Kupiłem w sklepie świeżą bułkę.
I bought a fresh bread roll at the store.
Here, 'bułkę' again denotes the bread roll, used in accusative case as the object of 'jadłem' (I ate).
Na śniadanie jadłem bułkę z serem.
For breakfast, I ate a bread roll with cheese.
The term 'bułkę' in this sentence expresses a desire for a bread roll, fulfilling an object role in accusative.