Learn Hardcore German: Wir warten im Zug, weil der Anschlusszug Verspätung hat. - We wait on the train because the connecting train is delayed.

You can say in dem Zug if you want to emphasize or be very clear, but in normal speech and writing people almost always use im Zug.
You cannot say in der Zug, because Zug is masculine (der Zug), so its dative form is dem, not der.

What case is im Zug, and how can I tell?

Im Zug is dative case.

Reasoning:

The preposition in can take either accusative (movement into) or dative (location).
Here it describes a location (in the train), not movement into it, so you use the dative.
Masculine dative of der Zug is dem Zug, and in dem contracts to im.

Why is the word order different in weil der Anschlusszug Verspätung hat?

Weil introduces a subordinate clause (a dependent clause expressing a reason). In German subordinate clauses, the finite verb goes to the very end of the clause.

So:

Main clause: Wir warten im Zug. → verb in 2nd position (warten).
Subordinate clause: weil der Anschlusszug Verspätung hat → verb (hat) at the end.

This verb-final rule applies after other subordinating conjunctions too, like dass, wenn, obwohl, damit etc.

Could I also say Wir warten im Zug, denn der Anschlusszug hat Verspätung? What’s the difference between weil and denn?

Yes, Wir warten im Zug, denn der Anschlusszug hat Verspätung is grammatically correct.

Differences:

weil is a subordinating conjunction → verb to the end: …weil der Anschlusszug Verspätung hat.
denn is a coordinating conjunction → normal main-clause word order: …denn der Anschlusszug hat Verspätung.

In everyday speech, weil is more common for “because”. Denn sounds a bit more formal or bookish and is less common in spoken language, but it’s not wrong.

Why is it Verspätung hat and not something like ist verspätet or ist zu spät?

All of these exist, but they’re used slightly differently:

hat Verspätung = literally “has delay” → very standard, neutral way:
- Der Zug hat 20 Minuten Verspätung. (The train is 20 minutes late.)
ist verspätet = “is delayed” → also correct, a bit more formal / technical sounding.
ist zu spät = “is too late” → more like “is late” in a general sense, not the classic railway phrase.

For trains, buses, planes etc., hat Verspätung is the most idiomatic everyday expression.

What exactly does Anschlusszug mean, and why der Anschlusszug?

Anschlusszug is a compound noun:

der Anschluss = connection
der Zug = train
→ der Anschlusszug = connecting train (the train you change to).

The whole compound takes the gender of the last part of the compound. The last part is Zug, which is masculine (der Zug), so you get der Anschlusszug.

Why is warten used without auf here? I thought it was auf etwas warten.

German allows both patterns:

warten alone (no object):
- Wir warten im Zug. = We’re waiting in the train.
  → Just states that you are waiting, without specifying for what.
auf etwas warten (with auf
- accusative):
- Wir warten im Zug auf den Anschlusszug.
  = We’re waiting in the train for the connecting train.

In your sentence, what you’re waiting for is explained indirectly in the weil-clause, so the speaker doesn’t use auf + object in the main clause.

Why is there a comma before weil?

German always puts a comma before a subordinate clause introduced by conjunctions like weil, dass, wenn, obwohl etc.

So:

Wir warten im Zug, weil der Anschlusszug Verspätung hat.

This comma rule is much stricter than in English; you can’t leave it out in standard written German.

Can I start the sentence with weil? How would the word order change?

Yes, you can front the weil-clause:

Weil der Anschlusszug Verspätung hat, warten wir im Zug.

Two things happen:

The verb in the weil-clause stays at the end (…Verspätung hat).
The finite verb warten in the main clause is still in 2nd position, so wir moves behind it: warten wir im Zug.

So you get: [Weil‑clause], [Verb–Subject–…].

Why are Zug, Anschlusszug, and Verspätung capitalized?

In German, all nouns are capitalized, no matter where they appear in the sentence.

So:

der Zug
der Anschlusszug
die Verspätung

Adjectives, verbs, and most other words are not capitalized, unless they start the sentence or are part of a proper name.

Why is it wir warten and not something like “we are waiting” form? Does German have a progressive tense?

German does not have a separate progressive tense like English “am waiting / is waiting”.

The simple present covers both:

Wir warten im Zug.
= We wait in the train.
= We are waiting in the train.

Context tells you whether it’s a general habit or something happening right now; here it clearly means “we are waiting right now”.

Can I move im Zug to another place in the sentence, like in English?

Yes, German word order is fairly flexible for adverbials like im Zug, as long as you respect verb positions. Some options:

Wir warten im Zug, weil der Anschlusszug Verspätung hat. (most natural)
Im Zug warten wir, weil der Anschlusszug Verspätung hat. (emphasis on in the train)
Wir warten, weil der Anschlusszug Verspätung hat, im Zug. (possible but sounds a bit clumsy; written style might avoid this).

The safest and most neutral version is the original: Wir warten im Zug, weil der Anschlusszug Verspätung hat.