هناك أربعة كتب.

Here, هناك is being used in an existential way, so it means there is / there are.

It is related to the ordinary meaning there, but in sentences like this it is not mainly about location. It introduces the idea that something exists or is present.

So:

• هناك كتاب = there is a book
• هناك أربعة كتب = there are four books

In other contexts, هناك can also simply mean over there.

Because in Arabic, the present tense usually does not use an explicit verb to be the way English does.

So where English says:

• There are four books

Arabic can simply say:

• هناك أربعة كتب

This is very normal in Arabic.

If you wanted a different tense, then a verb can appear:

• كان هناك أربعة كتب = there were four books
• سيكون هناك أربعة كتب = there will be four books

This is because numbers 3–10 in Arabic show gender polarity: the number takes the opposite gender of the noun it counts.

The singular of كتب is كتاب, and كتاب is masculine.

So with a masculine noun, you use the feminine-looking form of the number:

• أربعة كتب = four books

Compare that with a feminine noun:

• أربع سيارات = four cars

So even though books is not feminine, the number appears in the opposite-gender form because that is how 3–10 work in Arabic.

Because after the numbers 3–10, Arabic normally uses the plural form of the counted noun.

So:

• ثلاثة كتب = three books
• أربعة كتب = four books
• خمسة كتب = five books

The singular is:

• كتاب = book

The plural كتب is a broken plural, and it is pronounced kutub.

So this sentence follows a very common Arabic pattern:

• number from 3–10
• then a plural noun

Because the phrase means four books, not the four books.

In Arabic, this kind of counted noun after 3–10 is normally indefinite, so you do not use ال here:

• أربعة كتب = four books

If you wanted to say the four books, you would say:

• الكتب الأربعة

So:

• هناك أربعة كتب = there are four books
• الكتب الأربعة هناك = the four books are there

Those are different meanings.

A fully vocalized version is:

هُناكَ أَرْبَعَةُ كُتُبٍ

More fully transliterated:

hunāka ʾarbaʿatu kutubin

Why?

• أربعةُ is in the nominative
• كتبٍ is genitive plural

The reason كتب is genitive is that after numbers 3–10, the counted noun is normally plural genitive.

In normal everyday Arabic writing, these short vowels and case endings are usually omitted, so you usually just see:

هناك أربعة كتب

A careful, fully vocalized pronunciation is:

hunāka ʾarbaʿatu kutubin

If you are reading in a less formal way without full case endings, many learners will say something like:

hunāka ʾarbaʿa kutub

Useful pronunciation notes:

• هناك = hunāka
• أربعة = ʾarbaʿa / in full inflected reading ʾarbaʿatu
• كتب = kutub

The letter ع in أربعة is the consonant ʿayn, which has no exact English equivalent.

Yes. That is also correct.

• هناك أربعة كتب
• يوجد أربعة كتب

Both can mean there are four books.

A simple way to think about the difference:

• هناك is a very common existential opener: there is/there are
• يوجد literally means something like exists / is found

Both are widely used in Modern Standard Arabic. For a beginner, هناك is often one of the first and most useful ways to express there is / there are.

No, not normally.

هناك أربعة كتب means that four books exist or are present: there are four books.

If you want to say The four books are there, the natural Arabic sentence is:

الكتب الأربعة هناك

That sentence is different in two important ways:

• الكتب is definite: the books
• الأربعة describes those books as the four

So word order and definiteness matter a lot here.

It happens with the numbers 3–10 in general.

For these numbers, Arabic usually does this:

1. the number comes first
2. the counted noun is plural
3. the counted noun is usually genitive
4. the number shows opposite gender from the singular noun

Examples with كتاب:

• ثلاثة كتب = three books
• أربعة كتب = four books
• خمسة كتب = five books

So أربعة كتب is not an isolated expression; it belongs to a broader, very important number pattern in Arabic.