Vraag de apotheker wanneer de huisartsenpost opent.

Because vraag is the imperative form of vragen. The imperative is used for commands, instructions, or directions.

So Vraag de apotheker ... means you are telling someone to do something.

A few related forms:

• vragen = to ask
• ik vraag = I ask
• jij vraagt = you ask
• vraag! = ask!

In instructions, Dutch often uses this bare imperative form very naturally.

Because with vragen, Dutch usually treats the person you ask as a direct object.

A very common pattern is:

iemand iets vragen = to ask someone something

So:

• Vraag de apotheker wanneer ... literally follows the pattern ask the pharmacist when ...

If you want to use aan, Dutch more naturally switches to another expression, such as:

• Stel de vraag aan de apotheker = ask the question to the pharmacist

So in this sentence, de apotheker is the normal choice.

Apotheker is the person: the pharmacist.

The place is de apotheek: the pharmacy.

This is a very common mix-up for English speakers, because English often uses pharmacy for the place and pharmacist for the person. Dutch makes the same distinction, but the words are easy to confuse:

• de apotheker = the pharmacist
• de apotheek = the pharmacy

Yes. Wanneer is correct and natural here because it asks at what time / when something happens.

You can also say:

• Vraag de apotheker hoe laat de huisartsenpost opent.

The difference is small:

• wanneer = when, more general
• hoe laat = what time, more specific

If you specifically want the clock time, hoe laat is slightly more precise. If you just want the opening moment in general, wanneer works very well.

Because wanneer de huisartsenpost opent is an embedded question or subordinate clause.

In Dutch subordinate clauses, the conjugated verb usually goes to the end.

So:

• main clause: De huisartsenpost opent om zes uur.
• embedded question: ... wanneer de huisartsenpost opent

That final position of opent is one of the most important Dutch word-order patterns to learn.

Huisartsenpost is a compound noun written as one word, which is very normal in Dutch.

It is made up of:

• huisarts = general practitioner / family doctor / GP
• -en- = linking element
• post = post, station, service point

A huisartsenpost is the out-of-hours GP service or urgent GP clinic, not an ordinary daytime doctor’s office.

Dutch forms these long compound nouns very often, so seeing one long word like this is completely normal.

Because Dutch usually writes compound nouns as a single word.

So English may write something like:

• GP service
• doctor’s office
• emergency clinic

But Dutch often combines the parts:

• huisarts
• ziekenhuis
• tandartspraktijk
• huisartsenpost

For English speakers, this can look intimidating at first, but it is a very regular feature of Dutch spelling.

Opent comes from openen and means opens.

So wanneer de huisartsenpost opent asks about the moment it starts being open.

You could also hear:

• wanneer de huisartsenpost open is

That means when the out-of-hours GP service is open. This can sound a little broader, as if you are asking about availability or opening hours in general.

So:

• opent = when it opens
• open is = when it is open

Both are possible in real life, but opent is very natural if the focus is the opening time.

Because both nouns are de-words.

In Dutch singular nouns with a definite article take either:

• de
• het

Here:

• de apotheker
• de huisartsenpost

Unfortunately, whether a noun is a de-word or a het-word often just has to be learned along with the noun itself. So it is best to memorize them together:

• de apotheker
• de huisartsenpost
• de apotheek

By itself, Vraag de apotheker ... is a neutral instruction. It is common in written directions, instructions, or advice.

If you want to sound more polite in direct conversation, Dutch often prefers something softer, for example:

• Kunt u de apotheker vragen wanneer de huisartsenpost opent?
• Zou u de apotheker kunnen vragen wanneer de huisartsenpost opent?

A more formal imperative with u is also possible:

• Vraagt u de apotheker wanneer de huisartsenpost opent.

But in everyday speech, the Kunt u ... version often sounds more natural and polite.

A useful rough guide is:

• apotheker: a-po-TEE-ker
• huisartsenpost: HUIS-art-sen-post

A few tips:

• In apotheker, the stress is on TEE.
• In huisartsenpost, the main stress is at the beginning: HUIS.
• Dutch ui in huis is a difficult vowel for English speakers, so do not worry if it takes practice.

If you say the sentence slowly in chunks, it becomes easier:

Vraag / de apotheker / wanneer / de huisartsenpost / opent.

Yes. It is a complete subordinate clause with:

• wanneer = question word
• de huisartsenpost = subject
• opent = finite verb

So the whole sentence has this structure:

• Vraag = imperative verb
• de apotheker = object
• wanneer de huisartsenpost opent = the thing you want the pharmacist to tell you

That is why the sentence feels a lot like the English pattern ask someone when ..., even though the Dutch word order inside the clause is different.