This is the 336th most frequent Turkish word.
kişiye
"To the person" or "to the individual."
Here, 'kişiye' is used as a dative form of 'kişi' (person), indicating direction towards someone, 'to the person'.
Bu mektubu doğru kişiye ulaştırmalıyız.
We must deliver this letter to the right person.
In this sentence, 'kişiye' indicates specification or exclusivity directed towards someone, 'to the individual'.
Bu teklif sadece belirli bir kişiye özeldir.
This offer is exclusive to only one particular person.
Here, 'kişiye' is used to reinforce the tailor-made aspect, meaning 'towards the individual' for personal application.