қадимтарин: oldest
Забони тоҷикӣ яке аз забонҳои қадимтарини Осиёи Миёна мебошад.
Tajik is one of the oldest languages in Central Asia.
Наврӯз яке аз қадимтарин идҳои тоҷикон ба шумор меравад.
Navruz is (counted as) one of the Tajik people’s oldest holidays.
Bonus:
қадим – old; қадимтар – older; қадимтарин – oldest
Қадим can also mean “ancient”, so қадимтарин is “the most ancient”. But it is also used for something not so old as in this article about the oldest cinema in Dushanbe, which is about 60 years old.