Learn Hardcore Dutch: Tom zet zijn pet af zodra hij het restaurant binnenloopt. - Tom takes off his cap as soon as he walks into the restaurant.

Afzetten literally means “to take off / remove (something you are wearing on your head)”.
Because it is separable, in a normal main clause the verb splits:
- Tom zet zijn pet af.
  - zet = conjugated part of afzetten
  - af = separable prefix, moved to the end of the clause

Other forms of the same verb:

Ik zet mijn pet af.
Hij zet zijn helm af.
Ik heb mijn pet afgezet. (perfect tense: the prefix stays attached in the past participle)

So Tom zet zijn pet af means: Tom takes his cap off, with a focus on the action of removing something from the head.

Can I also say Tom doet zijn pet af or Tom neemt zijn pet af? Are they different from Tom zet zijn pet af?

All three are understandable, but they differ a bit in naturalness and nuance:

Tom zet zijn pet af.
- Very natural and common for hats, caps, helmets.
- Pairs nicely with opzetten (Tom zet zijn pet op = Tom puts on his cap).
Tom doet zijn pet af.
- Also common and correct.
- Doen … af (afdoen) is more general: you can say it for clothing, jewelry, accessories:
  - Hij doet zijn jas af.
  - Ze doet haar ring af.
- For a hat, both zet … af and doet … af sound fine.
Tom neemt zijn pet af.
- Also possible, but sounds a bit more formal or literary in many contexts.
- Often used in the figurative sense: zijn hoed afnemen voor iemand = to show respect/admiration to someone.

In everyday speech, Tom zet zijn pet af and Tom doet zijn pet af are the most typical choices. For this style of sentence, zet … af is very idiomatic.

Why do we use zijn pet here? Could we say Tom zet de pet af instead?

Zijn here is a possessive pronoun meaning his:

zijn pet = his cap

Using zijn makes it clear that the cap belongs to Tom.

You could say Tom zet de pet af, but that would usually suggest some specific cap already known in the context, not necessarily his own. For example:

Tom zet de pet af die hij van zijn opa heeft gekregen.
Tom takes off the cap that he got from his grandfather.

So:

Tom zet zijn pet af. = normal, neutral: we assume it’s his own cap.
Tom zet de pet af. = more context‑dependent; might sound a bit odd if no specific cap has been mentioned.

Also note the difference with the verb zijn (to be):

zijn pet (possessive his) vs.
hij is / Tom is (verb to be)

They look the same in spelling (zijn), but function differently in the sentence.

What exactly does zodra mean, and how is it different from als or wanneer?

Zodra means “as soon as” and expresses that one action happens immediately after another.

Tom zet zijn pet af zodra hij het restaurant binnenloopt.
= Tom takes off his cap as soon as he enters the restaurant.

Compared to other conjunctions:

als
- Very common, often means when / if.
- Time: Als hij thuiskomt, gaat hij eten.
- Condition: Als het regent, blijf ik thuis.
wanneer
- Similar to als, can mean when (time) or sometimes if (more formal or written style).
zodra
- More specific: immediately after the moment that…
- Often implies a quick, almost automatic reaction:
  - Zodra hij thuiskomt, gaat hij eten. = He eats right away when he gets home.

In this sentence, zodra emphasizes that Tom takes off his cap immediately when he enters, not some time later.

Why does the verb go to the end in zodra hij het restaurant binnenloopt?

Because zodra introduces a subordinate clause.

In Dutch:

A main clause (no subordinating conjunction) has:
- Subject – conjugated verb – …
- Example: Hij loopt het restaurant binnen.
A subordinate clause (after words like zodra, omdat, dat, als, wanneer) usually has:
- Conjunction – subject – other elements – verb cluster at the end
- Example: zodra hij het restaurant binnenloopt

So in your sentence:

Main clause: Tom zet zijn pet af
Subordinate clause: zodra hij het restaurant binnenloopt

In the subordinate clause, the verb binnenloopt is placed at the end, which is standard Dutch word order for this type of clause.

Why is it binnenloopt and not loopt binnen in this sentence?

Binnenlopen is a separable verb:

binnenlopen = to walk in / to walk into (a place)

How it behaves:

Main clause (no subordinating conjunction):
The verb splits:
- Hij loopt het restaurant binnen.
  - loopt (conjugated verb in second position)
  - binnen (separable part at the end)
Subordinate clause (after zodra, omdat, als, etc.):
The verb usually stays together at the end:
- zodra hij het restaurant binnenloopt
- omdat hij het restaurant binnenloopt

So:

Hij loopt het restaurant binnen. (main clause)
zodra hij het restaurant binnenloopt (subordinate clause)

That’s why you see binnenloopt as one word at the end in this sentence.

Why is the present tense binnenloopt used, even though in English we often think about the future with “as soon as he walks in”?

In Dutch, after time‑conjunctions like zodra, als, wanneer, the present tense is often used even for future events.

Compare:

Zodra hij het restaurant binnenloopt, zet hij zijn pet af.
Literally: As soon as he walks into the restaurant, he takes off his cap.
This can refer to a future situation (for example, a rule or habit).

Dutch typically does not use zal / zullen in this kind of subordinate time clause:

✗ Zodra hij het restaurant zal binnenlopen, … (sounds wrong/unnatural)
✓ Zodra hij het restaurant binnenloopt, …

So: present tense in Dutch with zodra covers what English might describe with a more future‑oriented meaning.

Why is it het restaurant and not de restaurant?

Every Dutch noun has a grammatical gender, which determines the article:

de‑words: use de
het‑words: use het

Restaurant is a het‑word:

het restaurant
de restaurants (plural always uses de)

There isn’t a simple rule for learners; you generally have to learn noun + article together:

het restaurant
het huis
de winkel
de straat

So het restaurant is correct because restaurant happens to belong to the het group in Dutch.

Does hij definitely refer to Tom here, or could it refer to someone else?

In Tom zet zijn pet af zodra hij het restaurant binnenloopt, Dutch speakers will normally understand hij as referring back to Tom, because he is the main person mentioned.

Grammatically, hij could refer to any masculine singular person mentioned in the context, for example:

Tom en Jan lopen over straat. Tom zet zijn pet af zodra hij het restaurant binnenloopt.
- Here, hij could be interpreted as Tom or Jan, depending on context and emphasis.

If you want to be 100% explicit that it’s Tom, you can repeat the name:

Tom zet zijn pet af zodra Tom het restaurant binnenloopt.

That sounds a bit heavy in Dutch if the context is already clear, so normally the simple hij is used and understood as referring to Tom.

How else could I say this sentence in Dutch without changing the meaning much?

A few natural alternatives:

Change the verb for “take off”:
- Tom doet zijn pet af zodra hij het restaurant binnenloopt.
Switch the order of the clauses:
- Zodra hij het restaurant binnenloopt, zet Tom zijn pet af.
- Zodra hij het restaurant binnenloopt, doet Tom zijn pet af.
Use a slightly different verb for “enter”:
- Tom zet zijn pet af zodra hij het restaurant ingaat.
- Tom zet zijn pet af zodra hij het restaurant binnenkomt.

All of these keep essentially the same meaning: he removes his cap immediately upon entering the restaurant.

Should there be a comma before zodra in this sentence?

In Dutch, a comma before zodra is optional but quite common, especially in written language:

Tom zet zijn pet af, zodra hij het restaurant binnenloopt.
Tom zet zijn pet af zodra hij het restaurant binnenloopt. (also correct)

General tendencies:

If the sentence is short and clear, many writers omit the comma.
If the sentence is longer or more complex, a comma can help readability.

When the zodra‑clause comes first, you almost always use a comma after it:

Zodra hij het restaurant binnenloopt, zet Tom zijn pet af.

So your original version is fine with or without a comma before zodra.