This is the 316th most frequent Greek word.
κανένα
"Κανένα" means "none" or "no" (used for neuter singular).
Here, "κανένα" is used with the word "πρόβλημα" to emphasize the absence of any problem.
Δεν υπάρχει κανένα πρόβλημα.
There is no problem.
Here, "κανένα" refers to neither option of the two books, emphasizing the negation of both possibilities.
Κανένα από τα δύο βιβλία δεν είναι καλό.
Neither of the two books is good.
In this sentence, "κανένα" is used to indicate that no person was seen, functioning as an indefinite pronoun.