A buli a házon belül van.

Because Hungarian uses the definite article a / az before both definite nouns here:

• a buli = the party
• a házon belül = inside the house / within the house

So the sentence is literally something like:

• the party the house-within is

This is normal in Hungarian. English does not repeat the in quite the same way, but Hungarian does.

Buli means party in an informal, everyday sense.

It is a common spoken word, similar to party in English when you mean a social event. It is less formal than some other possible words, so it sounds natural in casual conversation.

So:

• A buli... = The party...

This is one of the most natural questions, because both can relate to being inside something.

• a házban = in the house
• a házon belül = inside the house / within the house

The difference is mainly one of style and emphasis:

• a házban is the plain, basic way to say in the house
• a házon belül stresses being within the boundaries of the house
• belül often sounds a bit more explicit, and sometimes a bit more formal or deliberate

So in many situations, A buli a házban van would also be possible and may sound more everyday.

Because belül is used with a noun that takes a case ending here, and that noun appears in the superessive form:

• ház = house
• házon = on the house / on house-form

In this expression, Hungarian says:

• a házon belül

even though the meaning is inside the house, not on the house.

This happens because some Hungarian postpositions go with nouns in specific case forms. So you should learn belül together with the pattern it uses, rather than trying to translate each piece word-for-word.

Belül means inside or within.

In this sentence:

• a házon belül = inside the house / within the house

It can describe physical space, but in other contexts it can also be more abstract, like within an organization or internally.

Hungarian often leaves out van in the present tense when you are simply saying that something is something:

• A buli jó. = The party is good.
• Ő tanár. = He/She is a teacher.

But when you talk about location or existence, van is normally used:

• A buli a házon belül van. = The party is inside the house.

So here van is necessary because the sentence is about where the party is.

Yes, but it is also very normal.

The neutral order is:

• A buli a házon belül van.

That means:

• topic: A buli = the party
• new information: a házon belül van = is inside the house

Hungarian word order is flexible, and changing it can change emphasis.

For example, if you strongly emphasize the location, you might hear something else in a different context. But the version you have is a straightforward, neutral sentence.

Usually, in an ordinary context, it means the party is physically inside the house.

But -on belül expressions can sometimes be used more abstractly in Hungarian, because belül can mean within in a broader sense.

Still, with ház here, most learners should understand it first as a physical location:

• The party is inside the house.

Yes, in the right context.

• bent = inside, indoors
• A buli bent van. = The party is inside.

This is natural when the location is already understood from context. For example, if people are deciding whether the party is outside or inside, bent van works well.

But A buli a házon belül van is more explicit because it states exactly what it is inside of.

Often, yes.

If you simply want to say The party is in the house, then:

• A buli a házban van.

is usually the most direct and everyday version.

A házon belül is still correct, but it can sound slightly more marked, more explicit, or more focused on the idea of being within the house rather than somewhere else.

So both are possible, but a házban is often the simpler everyday choice.

A helpful breakdown is:

• A = the
• buli = party
• a = the
• házon belül = inside the house / within the house
• van = is

So the whole sentence means:

• The party is inside the house.

Even though the Hungarian structure is not identical to English, that is the natural meaning.

Hungarian has two forms of the definite article:

• a
• az

Which one you use depends on the sound that follows.

• a before a consonant sound: a buli
• az before a vowel sound: az autó

Since both buli and házon begin with consonants, the article is a in both places.

A simple learner-friendly pronunciation guide is:

• aw BOO-lee aw HAA-zhon beh-LOOL vawn

A few useful notes:

• u in buli is like oo
• á is a long vowel, so ház has a longer a sound
• ül in belül has the Hungarian ü, which does not exist in normal English pronunciation, so learners usually need practice with it

If you cannot say ü yet, that is normal for beginners. The most important thing at first is to recognize the word and remember its meaning and pattern.