How is fluviu different from râw?
"Fluviu" (dexonline, wikipedia) is a BIG river which flows into the sea or into the ocean. Such as the Nile, Amazon, Mississippi, Volga, Danube, etc. You know, the "BIG" ones.
"Râu" can be any other river.
as it is not specified, also accept "bad"
râu = river
rău = bad