"This is not common."
Translation:Ini tidak umum.
'umum' = public, general, common.
'biasa' = usual, regular, common.
These words are sometimes interchangeable, like in this sentence here :
But they're not 100% interchangeable.
toilet umum = public toilet.
'toilet biasa' doesn't work here, that would mean something like a plain/common toilet.
angkutan umum = public transportation.
angkutan biasa, doesn't work here for the same reason.
How would you say the opposite of rare?
I think I would use 'biasa', but it depends on the context.
'Saya jarang minum bir.' = I rarely drink beer.
'Saya biasanya minum teh.' = I usually drink tea.