Duh je u staroj kući.

• Duh = ghost or spirit
• je = is
• u = in
• staroj = old
• kući = house

A very literal breakdown is: Ghost is in old house.

Because after the preposition u meaning in for a location, Serbian uses the locative case.

So:

• basic form: stara kuća = old house
• locative form: u staroj kući = in the old house

Both the adjective and the noun change:

• stara → staroj
• kuća → kući

This happens because adjectives must agree with the noun in gender, number, and case.

Kući is the locative singular form of kuća.

In this sentence:

• kuća is feminine singular
• after u with the meaning of location, it becomes kući

So:

• kuća = house
• u kući = in the house

Staroj is the feminine singular locative form of the adjective star = old.

It matches kući, because Serbian adjectives agree with the noun they describe.

Here is the agreement:

• noun: kući → feminine, singular, locative
• adjective: staroj → feminine, singular, locative

So staroj kući is a matched adjective + noun phrase.

Not always. U can take either locative or accusative, depending on meaning.

• u + locative = location, being somewhere
  
  • u staroj kući = in the old house
• u + accusative = motion into somewhere
  
  • u staru kuću = into the old house

So in your sentence, the ghost is already there, so Serbian uses the locative.

Because je is a clitic in Serbian. Clitics usually come in the second position of the clause.

So:

• Duh je u staroj kući. is normal and natural.

The word je cannot usually stand freely wherever you want. It tends to come after the first stressed word or phrase.

This is a very common Serbian pattern, especially with forms like:

• je
• sam
• si
• se
• ga
• mu

Yes. Serbian word order is more flexible than English, although the meaning stays similar.

For example:

• Duh je u staroj kući. = neutral statement
• U staroj kući je duh. = puts more focus on in the old house
• U staroj kući duh je. = possible, but more marked or poetic

Even when the order changes, the clitic je still tends to stay in second position.

Because Serbian does not have articles like English a and the.

So Duh je u staroj kući could mean:

• The ghost is in the old house
• A ghost is in an old house
• The ghost is in an old house

Usually the context tells you which meaning is intended.

A simple guide:

• duh: roughly dooh, but with a clearly pronounced h at the end
• staroj: roughly STAH-roy, with j pronounced like English y
• kući: roughly KOO-chee, but ć is softer than English ch

A few useful pronunciation notes:

• j = English y
• h is pronounced, unlike in many English words
• ć is a soft Serbian consonant, somewhere between t and ch for many English speakers

Duh is a masculine noun.

In this sentence it is in the nominative singular, because it is the subject:

• Duh = the ghost / a ghost

So the structure is:

• Duh = subject
• je = verb
• u staroj kući = location

It can mean both ghost and spirit, depending on context.

For example:

• in a scary story, duh often means ghost
• in a religious or abstract context, it can mean spirit

So the word is broader than just one English translation.

Because that is the normal word order in Serbian for adjectives.

So:

• stara kuća = old house
• u staroj kući = in the old house

Putting the adjective after the noun is unusual and usually sounds poetic, literary, or strongly marked.

You would change the phrase after u to the accusative:

• Duh ide u staru kuću.

Compare:

• Duh je u staroj kući. = The ghost is in the old house.
• Duh ide u staru kuću. = The ghost is going into the old house.

This is a very important Serbian contrast:

• location → locative
• movement toward/into → accusative