German Infinitive Clauses with "zu" (um... zu, ohne... zu)
In German, connecting two verbs often requires the particle "zu". While English casually strings infinitives together with "to" ("I want to go", "I try to learn"), German follows strict architectural rules: modal verbs reject zu, separable prefixes swallow it in the middle (einzukaufen), and subordinate infinitive clauses demand comma separation and final verb placement.
⚡ The 3 Golden Conjunctions
1. The Subject Identity Requirement (Identität des Subjekts)
You can ONLY use an infinitive clause with um... zu if the subject of both clauses is identical! If the subjects are different, you MUST use a finite clause with damit:
"Ich beeile mich, um [ich] den Zug nicht zu verpassen."
(I hurry in order [for me] not to miss the train.)
"Ich gebe dir Geld, damit du ein Buch kaufst."
(I give you money so that you buy a book. *"um ein Buch zu kaufen" would mean I am buying it!)
2. Separable Verbs: The "zu" Sandwich
When the infinitive verb has a separable prefix (einkaufen, aufstehen, mitkommen), the particle zu is inserted directly between the prefix and the verb stem as a single merged word:
| Infinitive | Wrong (English Calque) | Correct "zu" Sandwich |
|---|---|---|
| einkaufen (to shop) | *zu einkaufen | einzukaufen |
| aufstehen (to get up) | *zu aufstehen | aufzustehen |
| mitbringen (to bring along) | *zu mitbringen | mitzubringen |
3. Verbs That Strictly FORBID "zu"
Never use zu with these verb families:
- All Modal Verbs: können, müssen, dürfen, sollen, wollen, möchten → "Ich kann schwimmen" (NEVER *zu schwimmen).
- Perception Verbs: sehen, hören, fühlen → "Ich höre sie singen".
- Movement Verbs: gehen, fahren → "Wir gehen essen".
- Lassen & Bleiben: "Er lässt das Auto reparieren".
🎯 Diagnostic Quiz: German "zu" Clauses
Which sentence is grammatically correct for "I forgot to call you"?