ouiboo

You don't, really. Swedish isn't a very helpful language, to the delight of punsters and crossword fans, and the dismay of everyone else. You just have to learn how the individual words are pronounced, and then figure out which one it's supposed to be by the context. The exception is some words with accents. Like idén (the idea) as opposed to iden (dens to hibernate in), or armén (the army) vs. armen (the arm). I have no idea why only some words get that extra clarification, since it would probably make the language a lot easier if it were more common.

Like gegegeno said, Finnish isn't like Swedish at all. It's about as easy for a Swede who hasn't learned Finnish to understand it as it is for Swedish is a North Germanic language, while Finnish belongs to a completely different family of Finno-Ugric languages. That's why Finland isn't considered to be a Scandinavian country, despite the geographic and historic closeness to Norway, Denmark, and Sweden. However, there is a minority of Swedish-speakers living in Finland, and schools there teach Swedish, so you might get some use out of your Swedish skills in Finland, too! As for Norwegian, yes, it's fairly easy to understand it. At least for most Swedes. The words and grammar are both very similar, though of course the level of comprehension won't be anywhere near as good as it is for a Norwegian. But even if you don't understand it right away, learning Norwegian would be a fairly easy journey if you start off fluent in another Scandinavian language. For me, personally, Danish is very difficult. I can barely understand a word of it when spoken, though written works better. Especially written 19th century Danish for some reason... Norwegian is much easier for most Swedes, in my experience. I think it's because the pronunciation is clearer than it is in Danish.