Learn Hardcore Dutch: Anna heeft helaas niet kunnen komen, omdat haar trein vertraging had. - Unfortunately, Anna could not come, because her train was delayed.

This sentence uses the perfect tense. Dutch often prefers the perfect (auxiliary hebben/zijn + participle or infinitive cluster) for specific past events. Although you could say the simple past (Anna kon helaas niet komen), the perfect (heeft kunnen komen) sounds more natural for a one‐time, completed action.

How do you form the perfect tense with a modal verb like kunnen?

Modal verbs don’t take a past participle in Dutch. Instead you use:
• Auxiliary (hebben)
• Bare infinitive of the modal (kunnen)
• Infinitive of the main verb (komen)
So you get heeft kunnen komen, not heeft gekund + participle.

Why is niet placed before kunnen rather than directly before komen?

In Dutch negation, niet usually precedes the verb (or verb cluster) it negates. Here the action is “be able to come” (kunnen komen), so you negate the whole cluster as niet kunnen komen.

What is the role of helaas in the main clause, and why is it positioned after heeft?

Helaas is a stance adverb meaning “unfortunately.” In a Dutch main clause (V2 word order), the finite verb is second, and stance adverbs typically follow it:
Anna (S) + heeft (V) + helaas (Adv) + …

Why does the subordinate clause begin with omdat and end with had?

Omdat is a subordinating conjunction (“because”), which pushes the finite verb to the end of the clause. Hence:
omdat + haar trein vertraging + had

Could you replace omdat with want, and what happens to the word order?

Yes. Want is a coordinating conjunction, so it does not send the verb to the end. You’d say:
Anna heeft helaas niet kunnen komen, want haar trein had vertraging.
Here had stays in second position.

Why is there no article before vertraging?

In transport contexts, vertraging (“delay”) is often used as an uncountable noun without an article:
haar trein had vertraging
You could add een vertraging to stress a specific delay, but it’s not required.

Could you also say omdat haar trein vertraagd was?

Yes, that’s a correct passive construction (vertraagd zijn), but Dutch speakers more commonly say haar trein had vertraging for vehicles and schedules.

What is the general word order for a verb cluster like niet kunnen komen in Dutch?

In an infinitive cluster you have:

Modal verb (kunnen)
Main verb (komen)
Negation (niet) goes before the cluster: niet kunnen komen.
With a perfect tense you add the auxiliary first: heeft niet kunnen komen.