Breakdown of Der Rasen ist heute Nachmittag zu mähen.
sein
to be
heute
today
der Nachmittag
the afternoon
zu
to (infinitive marker)
Questions & Answers about Der Rasen ist heute Nachmittag zu mähen.
The lesson is about using 'gehören' for passive alternatives. Why does this sentence use 'ist ... zu mähen' instead?
sein + zu + infinitive is another major passive alternative that expresses necessity. It means the exact same thing as Der Rasen gehört heute Nachmittag gemäht. The gehören structure is more colloquial and heavily used in southern Germany and Austria, while ist ... zu mähen is slightly more formal and standard across all German-speaking regions.
How would I say this using the standard passive voice with a modal verb?
You would use the modal verb müssen (must) combined with the regular passive: Der Rasen muss heute Nachmittag gemäht werden. The structure used in this sentence just provides a more concise, slightly more formal way to state the exact same requirement.
Does 'sein' + 'zu' + infinitive always mean something must be done, or can it mean it can be done?
It can mean either necessity (must/should) or possibility (can), depending entirely on the context. Here, because a lawn requires maintenance, it clearly means it must be mowed. However, in a sentence like Das Problem ist leicht zu lösen (The problem is easy to solve), the structure expresses possibility.
Why does heute Nachmittag come before zu mähen?