Quote Originally Posted by Throbert McGee View Post
Домой is actually an adverb, meaning that it doesn't decline or show gender, etc. -- it's always домой. And it means "to one's own home", or "homeward", etc.

The noun дом can often be translated "house; home", but in some contexts it can mean simply "a building." So if you said Я иду в дом (with дом in the accusative) it would generally be understood to mean "I'm going into the building." But Я иду домой has the clear meaning "I'm going home; I'm going to my own house" (not into some other building, and not into someone else's home). The same basic distinction applies to the adverb дома ("at home, in one's own house") versus the prepositional/locative phrase в доме ("inside a building").

To answer your other question, Europe is in the accusative because the accusative, by nature, is associated with motion towards a place. The prepositional/locative case, в Европе, expresses static location rather than destination -- "where at", rather than "where to".

And the distinction between the accusative and prepositional cases not only exists with "true" Verbs Of Motion (like идти and ехать) but also with other verbs that express some kind of movement, even if they're not technically VOMs.

For example, "I was sitting in the chair" (location without movement) would be Я сидел на стуле (with the word for chair in the prepositional/locative form).

But "She sat the child down in the chair" (movement into a position) would be Она посадила ребёнка на стул (with the word for "chair" in the accusative). Note that the verbs for "to be in a sitting position" vs. "to sit someone else in a seat" are also different, but the main point here is that the word for "chair" will be in different cases depending on whether you're talking about "where at?" (prepositional) or "where to?" (accusative).

And, by the way, if you're getting out of a chair and standing up ("where from?") then the word would be in the genitive (стула). So, to summarize:

"where at?" = prepositional case (but after certain prepositions, instrumental)
"where to?" = accusative case (but after certain prepositions, dative or instrumental)
"where from?" = genitive case (nearly always)
Oh, thanks a lot, that really helps me! Many thanks! I'll write that down so I won't forget.