Ek weet nie die rede vir haar vraag nie.

This is one of the most important features of Afrikaans negation.

In a basic negative sentence, Afrikaans usually uses double negation:

• the first nie comes after the verb or the element being negated
• the second nie usually comes at the end of the clause

So:

• Ek weet nie ... nie. = I do not know ...

In this sentence:

• Ek weet nie die rede vir haar vraag nie.

the first nie follows weet and the second nie closes the sentence.

This pattern is very normal in Afrikaans.

Because standard Afrikaans normally needs the full negative pattern with two nie words in a sentence like this.

So the correct structure is:

• Ek weet nie ... nie

If you leave out the first nie, the sentence sounds ungrammatical in standard Afrikaans.

Afrikaans has two common verbs that can both relate to knowing, but they are used differently:

• weet = to know a fact, piece of information, answer, reason, truth, etc.
• ken = to know a person, place, or be familiar with something

Here, the speaker is talking about knowing the reason for something, so weet is correct.

Examples:

• Ek weet die antwoord. = I know the answer.
• Ek ken haar. = I know her.

So:

• Ek weet nie die rede ... nie is correct because a reason is information, not a person or place.

Die means the, while 'n means a/an.

The sentence uses die rede because it refers to a specific reason:

• the reason for her question

If you said 'n rede, it would mean a reason, which is less specific.

Compare:

• Ek weet nie die rede nie. = I do not know the reason.
• Ek weet nie 'n rede nie. = I do not know a reason.
  This is possible in some contexts, but it is less natural here.

Here vir means for.

So:

• die rede vir haar vraag = the reason for her question

This is a very common pattern:

• die rede vir die probleem = the reason for the problem
• die rede vir sy vertrek = the reason for his departure

English speakers sometimes expect other prepositions, but with rede, vir is the normal choice when you mean reason for.

Because haar is the possessive form meaning her.

Compare:

• sy = she / his
• haar = her

This is a very important distinction:

• sy vraag = his question
• haar vraag = her question

So in this sentence:

• haar vraag means her question

Here it is a noun.

• vraag as a noun = question
• vra as a verb = to ask

So:

• haar vraag = her question
• Sy vra 'n vraag. = She asks a question.

This is a useful pair to remember:

• vraag = question
• vra = ask

The sentence follows normal Afrikaans main-clause order:

• Ek = subject
• weet = verb
• nie = first negative marker
• die rede vir haar vraag = object / rest of the sentence
• nie = final negative marker

So the pattern is:

• Subject + verb + nie + object/complement + nie

That gives:

• Ek weet nie die rede vir haar vraag nie.

Yes. The sentence is correct, but in everyday speech Afrikaans speakers might often say something like:

• Ek weet nie hoekom sy vra nie. = I do not know why she is asking.
• Ek weet nie hoekom sy gevra het nie. = I do not know why she asked.

Your original sentence is a bit more formal or abstract because it uses die rede vir haar vraag.

So:

• Ek weet nie die rede vir haar vraag nie. = correct, slightly more formal/book-like
• Ek weet nie hoekom sy vra nie. = very natural in conversation

Yes, sometimes it can, depending on context.

Most often:

• vraag = question

But in some contexts it can also mean a request or demand. In this sentence, though, the meaning is clearly question, especially because of the structure die rede vir haar vraag.

A learner should usually understand vraag first as question, unless the context shows otherwise.

You could add emphasis in a few ways, for example:

• Ek weet regtig nie die rede vir haar vraag nie. = I really do not know the reason for her question.
• Ek weet glad nie die rede vir haar vraag nie. = I absolutely do not know the reason for her question.

Here:

• regtig = really
• glad nie = not at all

Both are common ways to strengthen the negative.

Yes, rede means reason, and the words are related historically.

A rough pronunciation guide is:

• rede ≈ REE-duh

The first syllable is stressed.
The final e is a schwa-like sound, similar to the a in English sofa.

So if you are reading the sentence aloud, a rough English approximation would be:

• Ek vate nee dee REE-duh feer haar fraakh nee

That is only approximate, but it can help at first.

Not directly in the exact same structure, because hoekom means why, so it changes the grammar.

You would not say:

• Ek weet nie hoekom vir haar vraag nie. ✗

Instead, you would build a different sentence, such as:

• Ek weet nie hoekom sy vra nie.
• Ek weet nie hoekom sy die vraag vra nie.

So:

• die rede vir haar vraag = the reason for her question
• hoekom sy vra = why she is asking

They express similar ideas, but with different grammar.