Start with the intended meaning
Recover a relative clause to check the meaning. A deadline or instruction can supply necessity; a word such as leicht can favor possibility. Preserve that distinction and the noun phrase’s adjective ending.
Advanced: necessity or possibility with zu
die noch zu prüfenden Rechnungen / ein leicht zu öffnender Deckel These are gerundive attributes: zu + Partizip I + adjective ending. The invoices still have to be checked; the lid can be opened easily. The noun is affected by the action, unlike an ordinary active Partizip I. Context decides between necessity and possibility. There is no universal translation as “must”. With separable verbs, the spelling follows the infinitive with zu: einzureichen → einzureichend → die einzureichenden Unterlagen.
These compressed forms are common in formal instructions and technical writing. For a spoken explanation, a relative clause with müssen or können is often clearer. A short form such as ein leicht zu öffnender Deckel can still be natural outside formal prose; register is a tendency, not a prohibition.
Apply the pattern in another context
die bis Montag zu unterschreibenden Verträge
The stated deadline supplies an obligation: contracts that must be signed by Monday.
ein leicht zu reinigender Filter
The phrase normally presents a possibility: a filter that can be cleaned easily.
Choose the form and explain the meaning
5. Expand: “ein leicht zu öffnender Deckel” with können.
ein Deckel, der leicht geöffnet werden kann. The gerundive has passive possibility here.
6. An instruction requires submission by Friday. Expand “die bis Freitag einzureichenden Unterlagen”.
die Unterlagen, die bis Freitag eingereicht werden müssen. The instruction supplies necessity.
Additional check 1. Expand ein leicht zu tragender Koffer with können.
Ein Koffer, der leicht getragen werden kann. This is passive possibility, not an instruction that someone must carry it.
Additional check 2. Complete after mit den: mit den noch zu prüf___ Angaben.
Mit den noch zu prüfenden Angaben. Zu prüfend- takes adjective ending -en in this dative plural phrase.
Start with the topic overview
German participial attributes: Partizip I and II · Find another grammar topic
Questions about this topic
Does a gerundive always mean must?
No. It can express passive necessity or possibility. Ein leicht zu öffnender Deckel normally expresses possibility.
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