Ребёнок боится призрака.

Because the verb бояться normally takes the genitive case, not the accusative.

So:

• призрак = nominative, the dictionary form
• призрака = genitive singular

That means Ребёнок боится призрака literally has the structure:

• Ребёнок = the child
• боится = is afraid
• призрака = of a ghost / of the ghost

This is one of those verbs in Russian whose object does not behave like a direct object in English.

Ребёнок is in the nominative case because it is the subject of the sentence — the one doing the action or experiencing the state.

So the sentence breaks down like this:

• Ребёнок — nominative subject
• боится — verb
• призрака — genitive object after бояться

Боится is the 3rd person singular present-tense form of бояться.

So it means:

• I am afraid → я боюсь
• you are afraid → ты боишься
• he/she is afraid → он/она боится
• the child is afraid → ребёнок боится

Because ребёнок is singular, the verb is singular too.

The basic verb is бояться. The ending -ся is a very common Russian verb ending, historically related to reflexive meaning.

With бояться, you should learn the whole verb as a fixed vocabulary item:

• бояться = to be afraid, to fear

In this verb, -ся is not something you should try to translate word-for-word every time. It is simply part of how the verb is formed.

Its forms include:

• боюсь
• боишься
• боится
• боимся
• боитесь
• боятся

Grammatically, ребёнок is treated as masculine singular, so verbs in the past tense and adjectives usually agree with it as masculine when the noun itself is used.

But in meaning, it refers to a child, so it can mean either a boy or a girl.

For example:

• маленький ребёнок = a small child
• ребёнок боится = the child is afraid

So grammatical gender and real-life gender are not always the same thing.

Yes. In Russian print, ё is often written as е, so you may see:

• ребёнок
• ребенок

They mean the same word.

However, the pronunciation is different from plain е: ё is pronounced like yo. So the word is pronounced roughly rye-BYO-nak.

For learners, it is very helpful when ё is written explicitly, because it shows the correct pronunciation and stress.

The stress is:

• ребёнок → stress on ё
• боится → stress on the final я sound: бои́тся
• призрака → stress on the first syllable: при́зрака

So roughly:

• reb-YO-nok
• ba-EET-sa
• PREE-zra-ka

Stress is very important in Russian because it is not always predictable.

Russian has no articles like a and the, so the sentence itself does not tell you that directly.

Depending on context, Ребёнок боится призрака could mean:

• The child is afraid of the ghost
• The child is afraid of a ghost
• A child is afraid of the ghost
• A child is afraid of a ghost

English needs an article, but Russian does not. Context decides.

Yes. Russian word order is more flexible than English because case endings show the grammatical roles.

The neutral order here is:

• Ребёнок боится призрака.

But you could also hear:

• Призрака боится ребёнок.
• Боится ребёнок призрака.

These versions may sound more marked or emphasize different parts of the sentence, but the endings still show that:

• ребёнок is the subject
• призрака depends on боится

So the basic meaning stays the same.

No, that would be ungrammatical in standard Russian.

After бояться, you need the genitive, so it must be:

• боится призрака

not

• боится призрак

A good habit is to memorize the verb together with its case pattern:

• бояться + genitive

For example:

• бояться собаки = to be afraid of a dog
• бояться темноты = to be afraid of the dark
• бояться призрака = to be afraid of a ghost

It can mean either, depending on context.

Ребёнок боится призрака can mean:

• The child is afraid of the ghost right now
• The child is afraid of ghosts / of this ghost in general

Russian present tense often covers both a current situation and a general state.

If you wanted a clearly completed idea such as got scared, Russian would usually use a different verb, for example испугаться:

• Ребёнок испугался призрака. = The child got frightened by the ghost.

So боится is about the state of being afraid, not the moment of becoming afraid.