Breakdown of Wenn abgelaufen, ist die Milch gefährlich.
sein
to be
die Milch
the milk
gefährlich
dangerous
wenn
if / when (conditional, not a question word)
Questions & Answers about Wenn abgelaufen, ist die Milch gefährlich.
How does the shortened clause Wenn abgelaufen work here?
This is an elliptical subordinate clause (verkürzter Nebensatz). It leaves out the subject and the conjugated verb to be more concise. The full version would be Wenn sie abgelaufen ist, ist die Milch gefährlich. This shortening is very common in warnings, instructions, or casual speech when the missing words are obvious from the rest of the sentence.
Why does the main clause start with the verb ist right after the comma?
Even though the subordinate clause is shortened to just two words (Wenn abgelaufen), it still occupies the entire first position of the sentence. Because German requires the conjugated verb of the main clause to be in position two, ist must immediately follow the comma.
Can I use this type of shortening with any verb?
It works best when the past participle acts like an adjective describing a state, such as abgelaufen (expired). Crucially, the implied subject of the shortened clause must be exactly the same as the subject of the main clause. Here, both rely on die Milch.
Why is the word abgelaufen rather than just gelaufen?