A vezeték és a csatlakozó a dobozban van.

That is a very common question.

Hungarian often does omit the 3rd-person form of to be in simple identifying or descriptive sentences:

• A doboz nagy. = The box is big.
• Ez egy csatlakozó. = This is a connector.

But in location and existence sentences, van is normally kept:

• A dobozban van. = It is in the box.
• A vezeték a dobozban van. = The wire is in the box.

So in this sentence, van appears because the sentence is saying where something is.

This is one of the first things an English speaker is likely to notice.

Many learners would expect vannak, and in fact A vezeték és a csatlakozó a dobozban vannak is also a very natural sentence.

The singular van can be used when the two items are being presented together as one set in one location. In practical or technical descriptions, speakers sometimes do this quite naturally.

So the short answer is:

• van = treats them more like a combined set
• vannak = makes the plural agreement more explicit

If you are unsure as a learner, using vannak is often the safer choice when you are thinking of two separate things.

It is made of:

• doboz = box
• -ban = in

So:

• dobozban = in the box

This ending is called the inessive case, and it expresses being inside something.

You will see the same pattern in other words:

• szobában = in the room
• autóban = in the car
• házban = in the house

This is due to vowel harmony, a major feature of Hungarian.

Very roughly:

• words with back vowels usually take -ban
• words with front vowels usually take -ben

doboz contains back vowels, so it becomes dobozban.

Compare:

• házban = in the house
• kertben = in the garden
• székben = in the chair

So the meaning of -ban/-ben is the same; the form changes to fit the vowels of the word.

Because both nouns are definite, and in Hungarian it is very normal to repeat the article with each noun in a list joined by és.

So:

• a vezeték = the wire
• a csatlakozó = the connector

Together:

• a vezeték és a csatlakozó = the wire and the connector

Repeating the article makes it clear that these are two separate definite items. That is the most straightforward and natural pattern for a learner to use.

Hungarian has two forms of the definite article:

• a before a consonant
• az before a vowel

Since vezeték, csatlakozó, and dobozban all begin with consonant sounds, the article is a:

• a vezeték
• a csatlakozó
• a dobozban

If the next word started with a vowel, you would use az:

• az autó
• az ablak
• az ajtó

So this is a pronunciation-based choice, not a difference in meaning.

Yes. Hungarian word order is much more flexible than English word order, and it often changes the emphasis rather than the core meaning.

The given sentence:

• A vezeték és a csatlakozó a dobozban van.

puts the wire and the connector in the topic position, and then tells you where they are.

You could also say:

• A dobozban van a vezeték és a csatlakozó.

That version puts more attention on the box or on the location first.

So the basic meaning stays similar, but the information structure changes.

Because each noun refers to one item:

• vezeték = one wire
• csatlakozó = one connector

The sentence is talking about two things because they are joined by és = and.

This is just like English:

• the wire and the connector

You do not need plural nouns there, because each individual noun is singular.

If Hungarian wanted to say the wires or the connectors, it would use plural endings:

• vezetékek = wires
• csatlakozók = connectors

Not always. Both are somewhat context-dependent, especially in technical language.

• vezeték can mean wire, cable, lead, line, or conductor, depending on context
• csatlakozó can mean connector, plug, terminal, or a similar connecting part

So the most natural English translation depends on the situation. In an electronics or hardware context, wire and connector are very plausible choices.

Yes. Some speakers would indeed prefer:

• A vezeték és a csatlakozó a dobozban vannak.

That version matches the idea of a plural subject more directly.

So if you encounter both van and vannak in similar sentences, do not be surprised. The difference is less about a change in basic meaning and more about how the speaker chooses to frame the two items: as a pair/set or as two separate things.