қадимтарин

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.

сафед

сафед: white

Ранги сафед аз бисёр рангҳо иборат аст – зард, норинчӣ, сурх, сабз, кабуд ва гулобӣ.
White is composed of many colours – yellow, orange, red, green, blue and purple.
Роҳи сафед!
Safe journey! (Literally – white road)


Bonus: 
Do you know what тиллои сафед is? You can use google image search to find out.
There is a cool way to say “very white” in Tajik – сап-сафед. There are also cool ways to say “very blue”, “very red” etc.
If you need practice with colours you can learn them here: Memrise – Tajik Colours

гузаранда

гузаранда: contagious, infectious

Илми тиб касалиҳоро ба ду навъ ҷудо мекунад: касалиҳои гузаранда ва касалиҳои нагузаранда.
Medical science divides illnesses into two types: infectious diseases and non-infectious diseases.


Bonus: 
Ask a friend to give you examples of infectious diseases and non-infectious diseases.
In English we can describe other things as being contagious, for example, laughter. In Tajik, can something other than a disease be contagious?