Learn Dutch: Wacht de chauffeur er in het magazijn op? - Is the driver waiting for it in the warehouse?

This sentence uses a split pronominal adverb. Together, er + op mean "for it". In Dutch main clauses, they usually split up. er steps in right after the verb and subject (Wacht de chauffeur), and the preposition op gets pushed to the end of the sentence. The place description (in het magazijn) fits perfectly in the gap between them.

Why do we use op here if the English translation says "waiting for it"?

Prepositions often don't translate word-for-word between English and Dutch. In Dutch, you don't wait for something (voor), you wait on something. The fixed verb phrase is wachten op (to wait for). Because of this, "waiting for it" becomes er ... op.

Could I just keep erop together at the end, like Wacht de chauffeur in het magazijn erop?

While you might occasionally hear native speakers keep them together in very casual speech, the standard rule is to split them. It sounds much more natural to Dutch ears to put er early in the sentence and push op to the end.

What if the driver was waiting for a person instead of an object? Would we still use er ... op?