Ужинать дома - why in genitive?

Question

In the sentence: > Моя подруга будет ужинать дома what means *дом* to be in genitive? I actually expect it to be in prepositional case with some preposition like *в*, is that wrong?

Answer 1

This word is not a noun in the form of a Genitive or Prepositional cases, but it is an adverb with a suffix "-a", like "слева", "справа". It is an adverb of place expressing location.

Answer 2

Дом is an irregular in Russian. Therefore - дома - is the correct form in prepositional case, to answer the question где? Домой is the same word in accusative case. Usually, this latter usage is combined with a verb of motion, which is what triggers the case change to accusative (the more common use with the word дом.)

Answer 3

In your context дома is not a noun in the genitive case, дома is an adverb indicating a location and answering the question "где?".

Answer 4

The word in the example you give above is not in Genitive Case. Дом is an irregular that forms according to its own rules. So, in your sentence - "Моя подруга будет ужинать дома" the last word is, in fact, in Prepositional Case. Дом also does not take prepositions for Prepositional Case.