How do you say ''Good morning.'' ''Good night.'' in Sinhala ?

Question

Answer

Good morning = Suba udasanak wewa 
Good night = Suba rathriyak wewa

Answer

Ah this one is easy ... ^o^
Good Morning – subha udasanak - සුභ උදෑසනක්
Good Night – subha rathriyak - සුභ රාත්‍රියක්

In here subha (සුභ) means good , auspicious or nice

So using the word subha we can construct many other sentences.
Ex: subha gaman - සුභ  ගමන් -  have a great journey

But the word subah (සුභ )  is too formal to be used elsewhere.
Usually Sinhalese use the word  Honda (හොඳ )  when they want to say that something is good.
Ex: 
Honda panak - හොඳ පෑනක්- Good pen
Honda pothak - හොඳ පොතක්   - Good book