"This is a rainy day" versus "Hilo rains." Why does this not read "This day rains"? Rainy, I believe is a different word in Hawaiian, so I think the construction of the sentence of "this is a rainy day" should look a little like 'Ouaua keia la. I must be missing something here.
When it's only one term, it can't be an equational sentence. But if it's two terms (and the first begins with either He or ‘O) then it's a sentence equating the two terms. If it was "He lā kēia ua" it would mean "This rain is a day." That didn't really make any sense to me, but I hope it demonstrates the grammatical difference.