When using “OOo:”:http://www.openoffice.org the language of a passsage is an attribute of the character formating. This seems silly until you have multilingual dictionaries installed. Then the words marked as Swedish are checked against a Swedish dictionary and Swedish alternatives are offered by the spellchecker. It looks like magic.
With that said, I’m surprised that Mälaren isn’t recognised. It’s like have “Thames” rejected by an Enlgish dictionary.