Hard

cứng

(resistant to pressure)

khó

(requiring a lot of effort to do or understand)

khó

(severe)

khó khăn

(demanding a lot of effort to endure)

khó khăn

(severe)

khó tính

(severe)

khốn khó

(demanding a lot of effort to endure)

mạnh

(of drink: strong)

rắn

(resistant to pressure)