Learn Hardcore German: Der Zug kommt pünktlich an.

Ankommen is a separable-prefix verb. In a main clause the prefix an detaches from the verb stem and moves to the end of the clause, while the finite verb kommt stays in second position. In a subordinate clause or in an infinitive construction the parts remain together (for example: …, weil der Zug pünktlich ankommt or pünktlich anzukommen).

Why is the verb kommt in the second position?

German main clauses follow the V2 rule: the finite verb must occupy the second position, regardless of what element (subject, adverb, object) comes first. Here the subject Der Zug is first, so kommt follows in second position.

Why is the article der used for Zug?

Zug is a masculine noun. As the subject of the sentence it takes the masculine nominative singular article der. If Zug were an object in accusative, you would use den instead.

Is pünktlich an adjective or an adverb here, and why isn’t it inflected?

In this sentence pünktlich functions as an adverb modifying the verb phrase kommt an, indicating when or how the train arrives. Adverbs in German remain uninflected. If pünktlich were describing a noun (for example ein pünktlicher Zug), it would be an adjective and take an ending.

Can I move pünktlich to the front of the sentence?

Yes. Adverbials can occupy the first position for emphasis. You would then say Pünktlich kommt der Zug an, still respecting the V2 rule (finite verb in second position).

How would this sentence look in a subordinate clause?

In a subordinate clause introduced by a conjunction like weil, the verb goes to the end and the separable prefix stays attached: …, weil der Zug pünktlich ankommt.

How do I express where the train arrives?

Add a prepositional phrase before the final prefix. For example: Der Zug kommt pünktlich am Bahnhof an (am = an + dem) or Der Zug kommt pünktlich in Berlin an. The choice of preposition and case depends on the location you want to specify.

Which auxiliary verb do I use for the perfect tense of ankommen?

For ankommen you use sein as the auxiliary, because it indicates a change of state or movement. In the perfect tense you would say Der Zug ist pünktlich angekommen.