A képernyő mellett van a billentyűzet és az egér.

It means the.

In Hungarian, the definite article is a or az, and the indefinite article is egy.

So:

• a / az = the
• egy = a / an

The first word is capitalized only because it starts the sentence. So A képernyő means the screen, not a screen.

Mellett means next to, beside, or by.

It comes after the noun because it is a postposition. English uses prepositions that go before the noun, but Hungarian often uses postpositions that go after it.

So:

• English: next to the screen
• Hungarian: a képernyő mellett

That is completely normal Hungarian word order.

Because mellett itself shows the relationship.

In this sentence, képernyő stays in its basic form, and mellett does the job of expressing next to.

So Hungarian can express location in two common ways:

• with a case ending on the noun, such as asztalon = on the table
• with a postposition, such as képernyő mellett = next to the screen

Here, Hungarian uses the second pattern.

That is a very common learner question.

Hungarian often leaves out van in the present tense when the predicate is a noun or adjective:

• A képernyő nagy. = The screen is big.
• Ez egy egér. = This is a mouse.

But van is normally not omitted when it expresses existence or location:

• Az egér az asztalon van. = The mouse is on the table.
• A képernyő mellett van a billentyűzet és az egér. = The keyboard and the mouse are next to the screen.

So in this sentence, van is needed because the sentence tells you where something is.

Because this sentence is built in a location-first, there-is/there-are-style way:

• A képernyő mellett van... = Next to the screen there is / are...

In this kind of structure, singular van is very common and natural, even when more than one item follows.

If you make the keyboard and the mouse the main subject at the front, then plural vannak becomes the more regular choice:

• A billentyűzet és az egér a képernyő mellett vannak.

So both the structure and the focus matter here.

Hungarian has two forms of the definite article:

• a before a consonant sound
• az before a vowel sound

Since egér begins with e, a vowel, it takes az:

• az egér

Compare:

• a billentyűzet
• a képernyő
• az egér

This is just like a sound-based choice; it does not show gender.

Because in Hungarian, when two definite nouns are joined by és (and), it is very normal to repeat the article before each noun.

So:

• a billentyűzet és az egér

is the most natural ordinary form.

English often says the keyboard and mouse, but Hungarian usually prefers the article with both nouns when both are definite.

Yes. Hungarian word order is flexible, and different orders can shift the focus.

The original sentence:

• A képernyő mellett van a billentyűzet és az egér.

puts the location first. It feels a bit like:

• As for next to the screen, that’s where the keyboard and the mouse are.

A more subject-centered version would be:

• A billentyűzet és az egér a képernyő mellett vannak.

That version puts more emphasis on the keyboard and the mouse as the topic.

So the sentence order is not random; it helps show what the speaker is focusing on.

Because each noun refers to one thing:

• a billentyűzet = the keyboard
• az egér = the mouse

The sentence has two singular nouns joined by and, not plural nouns.

If you meant more than one of each, you would need plural forms, such as:

• billentyűzetek
• egerek

So this sentence means one keyboard and one mouse.

Usually, for a normal neutral sentence like this, the articles are the natural choice:

• A képernyő mellett van a billentyűzet és az egér.

If you remove them, the sentence sounds more indefinite, telegraphic, or label-like, and in many contexts less natural for a beginner’s standard Hungarian.

Using the articles here tells the listener that we are talking about specific, identifiable objects: the screen, the keyboard, and the mouse.