This is the 2546th most frequent Polish word.
piosenki
Songs.
Here, 'piosenek' refers to the plural form in the genitive case, as the verb 'słucham' governs it in this form.
Słucham nowych piosenek w radiu.
I listen to new songs on the radio.
In this sentence, 'piosenki' is the plural form in the nominative case, serving as the subject of the sentence.
Te piosenki są bardzo popularne.
These songs are very popular.
Here, 'piosenki' is in the plural form and appears in the nominative case as part of the predicate.