A kapcsoló az ajtó mellett van, ezért sötétben is könnyű megtalálni.

They are both the Hungarian definite article, equivalent to the.

• a is used before a consonant sound: a kapcsoló
• az is used before a vowel sound: az ajtó

So the choice depends on pronunciation, not on gender or case.

Hungarian usually uses postpositions, not prepositions. That means the location word comes after the noun phrase.

• ajtó = door
• mellett = beside / next to

So:

• az ajtó mellett = next to the door

English says next to the door, but Hungarian literally has something more like the door next-to.

No. mellett is a postposition, and in this sentence the noun stays in its basic form:

• az ajtó mellett

Many Hungarian location expressions work this way: article + noun + postposition.

So you do not add something like -ban/-ben to ajtó here.

That is a very common question. Hungarian often omits van in the present tense when the predicate is a noun or adjective:

• A kapcsoló új. = The switch is new.
• A ház nagy. = The house is big.

But when you express location, van is normally used:

• A kapcsoló az ajtó mellett van. = The switch is next to the door.

So here van is necessary because the sentence says where the switch is.

ezért means therefore, for this reason, or that’s why.

It connects the second clause to the first:

• A kapcsoló az ajtó mellett van, ezért...
• The switch is next to the door, therefore / that’s why...

So the second part gives the consequence of the first part.

sötétben means in the dark.

It contains the ending -ben, which means in.

• -ban / -ben = in
• sötét = dark / darkness in this kind of expression

So sötétben is an idiomatic way to say in the dark.

This is a very natural Hungarian expression.

Here is means also, too, or in context often even.

So:

• sötétben is = also in the dark / even in the dark

The idea is that it is easy to find the switch not only under normal conditions, but even when it is dark.

A useful point: is usually comes after the word or phrase it belongs to. Here it belongs to sötétben.

Because Hungarian often uses an adjective + infinitive structure for it is easy to do something.

• könnyű megtalálni = it is easy to find

Here könnyű is an adjective meaning easy.

By contrast, könnyen is an adverb meaning easily. That would be used in a different type of sentence, for example:

• Könnyen megtalálom. = I can find it easily.

So in your sentence, könnyű megtalálni is the normal way to say easy to find.

Because meg- is a verbal prefix that often gives the sense of a completed or successful action.

• találni = to find, to come across
• megtalálni = to find successfully, to locate

In this sentence, the meaning is specifically that the switch is easy to locate, so megtalálni is the natural choice.

Also, the prefix is written together with the infinitive here:

• megtalálni

It only separates in certain sentence patterns.

It is not stated explicitly, because Hungarian often leaves pronouns out when they are clear from context.

Here megtalálni means to find it, and it clearly refers back to a kapcsoló.

So Hungarian does not need to say a separate word for it here. English usually does.

By itself, kapcsoló can mean switch in a general sense. In this sentence, because it is next to the door and easy to find in the dark, the natural interpretation is light switch.

If you want to be more explicit, Hungarian can also say:

• villanykapcsoló = light switch

But in everyday speech, kapcsoló is often enough when the context makes it obvious.

Hungarian word order is flexible, but it is strongly influenced by focus and information structure.

This order is natural and neutral here:

• sötétben is sets the condition: even in the dark
• könnyű gives the main statement: it is easy
• megtalálni completes it: to find

So the phrase flows as:

• therefore, even in the dark, it is easy to find

You could change word order in Hungarian for emphasis, but this version sounds natural and straightforward.

Because the sentence contains two clauses:

• A kapcsoló az ajtó mellett van
• ezért sötétben is könnyű megtalálni

The comma helps separate the first statement from the consequence introduced by ezért.

So the punctuation works much like English punctuation in a sentence with therefore or that’s why.