V tom domě je duch.

Because after the preposition v meaning in, Czech normally uses the locative case for location.

So the words change form:

• ten → tom
• dům → domě

That is why you get:

• v tom domě = in that house

Using v ten dům would be incorrect here, because those are not the right case forms after v when you are talking about being in a place.

It is the locative singular.

More specifically:

• tom is the locative singular form of ten
• domě is the locative singular form of dům

Czech uses the locative after certain prepositions, including v when it means location.

So:

• dům = basic dictionary form, nominative
• v domě = in the house, locative

Because Czech nouns change endings depending on their grammatical role.

Here, dům is after the preposition v, and that requires the locative when you mean location. The locative singular form of dům is domě.

So the pattern is:

• dům = house
• v domě = in the house

This kind of change is very common in Czech and is a core part of the case system.

Tom is the correct form of the demonstrative ten in the locative singular masculine/neuter.

Since dům is a masculine noun, the demonstrative has to match it in gender, number, and case.

So:

• ten dům = that house
• v tom domě = in that house

You cannot use ten here because ten is nominative, not locative.

Je is the 3rd person singular form of být, which means to be.

So:

• je = is

In this sentence, duch is singular, so Czech uses je, not a plural form.

Structure:

• V tom domě = in that house
• je = is
• duch = ghost

So literally: In that house is a ghost.

Here duch is the subject of the sentence, so it stays in the nominative singular, which is the basic form.

The sentence is basically saying:

• A ghost is in that house or
• There is a ghost in that house

Since duch is the thing that is, it appears in the nominative:

• duch = ghost

Not every noun in a sentence changes form—only the ones whose grammatical role requires it.

Czech does not have articles like English a and the.

So duch can mean:

• a ghost
• the ghost

Which one is meant depends on context.

In this sentence, English would usually translate it as a ghost, because the sentence introduces the ghost as new information.

Similarly, v tom domě often corresponds to in that house, because tom already gives a definite, pointing meaning.

Czech word order is more flexible than English word order, because cases show grammatical relationships.

Starting with V tom domě puts emphasis on the place first. It sounds natural if the speaker wants to say what is in that house.

Compare:

• V tom domě je duch. = In that house, there is a ghost.
• Duch je v tom domě. = The ghost is in that house.

The first version often presents duch as new information. The second version can sound more like you already know about the ghost, and now you are being told where it is.

Yes. V tomto domě je duch is also correct.

The difference is mostly stylistic:

• v tom domě = in that house
• v tomto domě = in this/that very house

Tomto is a fuller, slightly more explicit form. In everyday speech, v tom domě is very common and natural.

So both are possible, but v tom domě is simpler and very normal in conversation.

A rough pronunciation is:

• v tom domě je duch
• approximately f tom do-mnye ye dookh

A few useful points:

• v is often pronounced like f before a voiceless consonant such as t, so v tom sounds close to f tom
• ě often softens the preceding consonant, so domě sounds roughly like dom-ye or dom-nye, depending on the consonant and the speaker
• ch in duch is the throaty sound heard in German Bach or Scottish loch

Also, Czech stress is usually on the first syllable of each word:

• V TOM do-mě je DUCH

Yes, it is a very natural Czech sentence.

Czech often expresses there is/there are simply with a form of být:

• je = is
• jsou = are

So instead of adding a separate word for there, Czech often just says:

• V tom domě je duch. = There is a ghost in that house.

That is a standard and idiomatic way to say it.