This is the 13667th most frequent Turkish word.
kutlasın
"Let him/her celebrate."
The word "kutlasın" is used in a subjunctive mood, expressing the wish for someone else to celebrate.
O, bu günü arkadaşlarıyla kutlasın.
Let him celebrate this day with his friends.
Here, "kutlasın" is used in plural subjunctive form, emphasizing a reasoned wish.
Kutlasınlar ki mutlulukları artsın.
Let them celebrate so that their happiness increases.
This usage of "kutlasın" conveys a blessing or hope for continuous celebration.