This is the 13110th most frequent Turkish word.
kartına
"To your card" or "onto your card."
Here, 'kartına' is used in the possessive sense with a dative case suffix '-a', indicating the indirect object ('to your card').
Kartına bir şey yazdım.
I wrote something on your card.
In this sentence, 'kartına' is in the dative case, showing the direction of attention ('to your card').
Kartına dikkat etmelisin.
You should pay attention to your card.
Here, 'kartına' again takes the dative case, showing the recipient or location ('to your card').