Why do we say: "Jag måste gå hem", instead of: "
So learning grammar is simply like buying tools when your building a house. You don't really need to know about all the rules when you finally know the language (how many kids speaking Swedish knows about nouns and adjectives?) just like you don't need all the tools when the house is done. But only a few people can build houses without tools!
So... do you want to know the grammatical answer to the qustion above?
Hem, instead of hemma is used togehter with verbs showing a direction (går, kommer, åker, flyger, flyttar...). We don't need to use the preposition till with these adverbs.
The form hemma is used togeher with all the verbs that show no direction (är, sitter, ligger...). We have a few of these direction adverbs. For a more thorough explanation, sign up for Swedish2go grammar- and language rules tutorial pack.