Nitko nije vidio duha.

Nitko means nobody or no one.

It is used for people, not things. For things, Croatian would use ništa = nothing.

Examples:

• Nitko nije došao. = Nobody came.
• Nitko me ne poznaje. = Nobody knows me.

Grammatically, nitko is singular.

In Croatian, this is normal. Croatian uses negative concord, which means that if the sentence is negative, several words in the sentence can be negative at the same time.

So:

• Nitko nije vidio duha.
  literally has two negatives, but it simply means Nobody saw the ghost.

This is standard Croatian grammar, not an error.

More examples:

• Nitko ništa ne zna. = Nobody knows anything.
• Nikad nisam bio tamo. = I have never been there.

An English speaker may feel this is a double negative, but in Croatian it is the correct pattern.

Nije is the 3rd person singular negative form of je / biti (to be) used as an auxiliary in the past tense.

Croatian past tense is often formed with:

• an auxiliary form of biti
• plus the l-participle

Here:

• nije = did not / has not as part of the past tense construction
• vidio = past participle meaning seen / saw

So:

• nije vidio = did not see

Compare:

• On je vidio duha. = He saw the ghost.
• On nije vidio duha. = He did not see the ghost.

Vidio agrees with the subject in gender and number.

The subject here is nitko, and although nitko means nobody, it is grammatically treated as singular, and in this kind of agreement it normally takes the masculine singular participle.

So:

• Nitko nije vidio... is correct.

Compare:

• Marija nije vidjela duha. = Marija did not see the ghost.
• Ljudi nisu vidjeli duha. = The people did not see the ghost.

So vidio is there because the sentence is built around a singular subject, nitko.

Because duha is the accusative singular form of duh.

Duh is a masculine animate noun. In Croatian, masculine animate nouns usually have:

• nominative singular = duh
• accusative singular = same form as the genitive singular, so duha

Since duha is the direct object of vidio, the accusative is needed.

So:

• duh = subject form
• duha = object form

Compare:

• Duh je nestao. = The ghost disappeared.
  Here duh is the subject.
• Vidio sam duha. = I saw the ghost.
  Here duha is the object.

Yes. In grammar, animate does not always mean biologically alive. It is a grammatical category.

Words for people, animals, and many beings treated like persons or creatures, including things like ghosts, are often grammatically animate.

That is why:

• duh → duha in the accusative

If the noun were masculine inanimate, the accusative would usually look like the nominative instead.

It is the Croatian past tense, often called the perfect (perfekt).

Structure:

• nije = auxiliary
• vidio = past participle

In English, this will often translate simply as:

• did not see

So:

• Nitko nije vidio duha. = Nobody saw the ghost.

Depending on context, Croatian past tense can sometimes overlap with English has not seen, but in a sentence like this, Nobody saw the ghost is the most natural translation.

Croatian normally does not use articles like English a and the.

So duha can mean:

• a ghost
• the ghost

The exact meaning depends on context.

That means the sentence could be understood as:

• Nobody saw a ghost or
• Nobody saw the ghost

If your learning material gives the ghost, that interpretation comes from context, not from a separate word in Croatian.

Yes. Croatian word order is fairly flexible, although Nitko nije vidio duha is a neutral, natural order.

Other orders are possible for emphasis, for example:

• Duha nitko nije vidio. = It was the ghost that nobody saw / Nobody saw the ghost.

This changes the focus or emphasis, not the basic meaning.

However, the position of clitic-like elements and auxiliaries follows rules, so not every imaginable order sounds equally natural. For a learner, Nitko nije vidio duha is the safest standard version.

They are very close in meaning, but for standard Croatian, nitko is the preferred form.

• nitko = standard Croatian
• niko = common in some speech and standard in some neighboring varieties

If you are learning standard Croatian, use nitko.

No. If you want a negative sentence, you need the negative auxiliary.

• Nitko nije vidio duha. = correct
• Nitko je vidio duha. = incorrect for this meaning

Also, because nitko is a negative word, Croatian normally requires the verb to be negative too:

• nitko ... nije not
• nitko ... je

So nije is essential here.