Waarvoor gebruik je deze markeerstift?

Waarvoor is the standard Dutch way to say what for / for what when asking about purpose.

Dutch often combines waar + a preposition:

• waarvoor = for what
• waarmee = with what
• waarin = in what
• waarop = on what

So in this sentence, Waarvoor gebruik je deze markeerstift? literally works like For what do you use this highlighter?

A very common alternative is:

• Waar gebruik je deze markeerstift voor?

That means the same thing and sounds very natural too.

Because this is a question.

In a normal statement, Dutch would say:

• Je gebruikt deze markeerstift ... = You use this highlighter ...

But in a direct question, the finite verb usually comes before the subject:

• gebruik je = do you use

So the structure is:

• Waarvoor
  • gebruik
    • je
      • deze markeerstift

This verb-subject inversion is very common in Dutch questions.

Both are forms of you, but they are used a little differently.

• je = unstressed, neutral, very common
• jij = stressed or emphasized

So:

• Waarvoor gebruik je deze markeerstift? = neutral, normal
• Waarvoor gebruik jij deze markeerstift? = puts extra emphasis on you, as in what do you use this highlighter for?

In everyday speech, je is usually the default unless you want contrast or emphasis.

Because markeerstift is a de-word: de markeerstift.

In Dutch demonstratives:

• deze is used with de-words and plural nouns
• dit is used with singular het-words

Examples:

• deze markeerstift = this highlighter
• dit boek = this book

So since it is de markeerstift, the correct form is deze.

Because deze already does the job of a determiner.

In Dutch, you normally use either:

• an article: de markeerstift or
• a demonstrative: deze markeerstift

Not both together.

So:

• de markeerstift = the highlighter
• deze markeerstift = this highlighter

But not:

• de deze markeerstift

Yes. Dutch very often writes compound nouns as one word.

Markeerstift is made up of:

• markeer- from markeren = to mark/highlight
• stift = pen, marker, writing stick

So markeerstift is literally something like marking pen.

This is very typical Dutch spelling. English often separates or hyphenates words more than Dutch does, but Dutch usually joins them:

• huisdeur = house door / front door
• theekopje = teacup
• markeerstift = highlighter

Yes, absolutely.

Both of these are correct and natural:

• Waarvoor gebruik je deze markeerstift?
• Waar gebruik je deze markeerstift voor?

The first keeps the preposition attached to waar:

• waarvoor

The second leaves voor at the end:

• waar ... voor

Both mean the same thing. Depending on region, style, and personal preference, one may sound slightly more natural than the other, but both are standard and common.

Sometimes you may hear:

• Voor wat gebruik je deze markeerstift?

People do say this, but waarvoor is generally the more standard and widely taught form.

So for learners, the safest choices are:

• Waarvoor gebruik je deze markeerstift?
• Waar gebruik je deze markeerstift voor?

Those are the most useful versions to remember.

It is the direct object: the thing being used.

Structure:

• Waarvoor = for what purpose
• gebruik = use
• je = you
• deze markeerstift = this highlighter

So the sentence is asking about the purpose of using that object.

You can swap parts while keeping the same basic pattern.

Examples:

• Waarvoor gebruik je dit mes? = What do you use this knife for?
• Waarvoor gebruik jij deze app? = What do you use this app for?
• Waarvoor gebruikt u deze machine? = What do you use this machine for? (formal)

This helps show the pattern:

• Waarvoor gebruik/gebruikt + subject + object?

It is informal/neutral because it uses je.

If you want to be formal or polite, you would usually say:

• Waarvoor gebruikt u deze markeerstift?

So:

• je = informal singular, and often also used in casual general speech
• u = formal/polite

The original sentence is perfectly normal in everyday conversation.