Ek twyfel daaraan.

Because Afrikaans verbs usually do not change form for different subjects.

So you get:

• ek twyfel = I doubt
• jy twyfel = you doubt
• hy/sy twyfel = he/she doubts
• ons twyfel = we doubt

This is much simpler than English, where you have I doubt but he doubts.

Twyfel is the verb. Its basic dictionary form is also twyfel, and in this sentence it is the present tense verb.

A useful pattern to remember is:

• twyfel aan iets = to doubt something
• twyfel aan iemand = to doubt someone

So in Ek twyfel daaraan, the verb is not standing alone; it is part of the pattern twyfel aan ...

Daaraan is a pronominal adverb. In simple terms, it is a compact Afrikaans way of saying something like to/about/of that/it, depending on the verb and preposition involved.

It is made from:

• daar = there / that
• aan = to / on / at

With twyfel aan, daaraan means about that / of that / it in the sense required by the verb doubt.

So:

• Ek twyfel daaraan literally works like I doubt about-that
• natural English: I doubt it

Because Afrikaans often combines daar-, hier-, or waar- with a preposition into a single word.

Examples:

• daaraan = about that / to that
• hieraan = about this / to this
• waaraan = to what / what ... to

This is completely normal in Afrikaans and is something learners see a lot.

You can sometimes say aan dit, but daaraan is usually the more natural and idiomatic choice when referring to a thing, idea, situation, or statement.

So for non-human referents:

• more natural: Ek twyfel daaraan
• possible but often less idiomatic: Ek twyfel aan dit

However, with a person, you do not use daaraan. You use the normal preposition + pronoun:

• Ek twyfel aan hom = I doubt him
• Ek twyfel aan haar = I doubt her

Normally, no.

Daaraan is typically used for things, ideas, facts, plans, statements, and similar non-person referents.

So:

• Ek twyfel daaraan = I doubt it / that
• Ek twyfel aan hom = I doubt him

That distinction is important.

When twyfel means doubt followed by a noun or pronoun, aan is the normal preposition:

• Ek twyfel aan die plan
• Sy twyfel aan hom
• Ons twyfel daaraan

But if a whole clause follows, Afrikaans often uses a different structure, for example:

• Ek twyfel of hy kom = I doubt whether he is coming

So the pattern depends on what comes after twyfel.

You use the usual Afrikaans double negative:

• Ek twyfel nie daaraan nie.

The basic placement is:

• first nie after the verb phrase
• second nie at the end of the clause

So:

• Ek twyfel daaraan. = I doubt it.
• Ek twyfel nie daaraan nie. = I do not doubt it.

In a yes/no question, Afrikaans usually puts the verb first:

• Twyfel jy daaraan? = Do you doubt it?

Compare:

• statement: Jy twyfel daaraan.
• question: Twyfel jy daaraan?

That verb-first pattern is very common in Afrikaans questions.

In a subordinate clause, the verb usually moves to the end:

• ... omdat ek daaraan twyfel = ... because I doubt it
• ... as sy daaraan twyfel = ... if she doubts it

So compare:

• main clause: Ek twyfel daaraan.
• subordinate clause: dat ek daaraan twyfel

This word order change is very common in Afrikaans.

The difference is roughly like that versus this.

• daaraan = about that / it
• hieraan = about this

Examples:

• Ek twyfel daaraan. = I doubt that / it.
• Ek twyfel hieraan. = I doubt this.

So if the speaker is referring to something nearer or more immediate, hieraan may be used instead.

Yes. A common alternative is to use betwyfel:

• Ek betwyfel dit.

This also means I doubt it.

The difference is roughly:

• twyfel aan = very common, built with a verb + preposition
• betwyfel = a single verb, often a bit more direct or formal

So both are useful, but Ek twyfel daaraan is a very natural everyday structure to know.