Lassen is deceptively small and astonishingly powerful. On its own it means "to leave" or "to let," but its real importance is grammatical: it builds the German causative ("to have something done") and a whole alternative to the passive (sich lassen). It is a strong verb with the a → ä change, and it triggers one of the two great double-infinitive constructions in the Perfekt. For an English speaker, mastering lassen is the difference between sounding like a textbook and sounding like a native.
Principal parts
| Infinitive | Präteritum | Partizip II (auxiliary) |
|---|---|---|
| lassen | ließ | gelassen (hat) |
Read this as lassen – ließ – hat gelassen. The Perfekt auxiliary is haben. Note the ß: the Präteritum is ließ (long vowel before ß), but the present lasse / lässt keeps the short vowel and double ss. Getting ss vs ß right here is pure orthography, and it follows the rule: ß after a long vowel or diphthong, ss after a short one.
Präsens (present)
Strong a → ä in the du- and er-forms. Because the stem lass- ends in -ss, the du-form does not add another s: it is simply lässt, identical to the er-form.
| Person | Form |
|---|---|
| ich | lasse |
| du | lässt |
| er / sie / es | lässt |
| wir | lassen |
| ihr | lasst |
| sie / Sie | lassen |
Lass mich kurz ausreden!
Let me finish what I'm saying! (informal du-command, very common)
Sie lässt ihren Sohn nicht allein nach Hause gehen.
She doesn't let her son walk home alone. (du- and er-form share the umlaut form lässt)
Präteritum (simple past)
The strong stem is ließ- (with ß). Like halten, lassen uses the Präteritum freely in writing and narrative.
| Person | Form |
|---|---|
| ich | ließ |
| du | ließest |
| er / sie / es | ließ |
| wir | ließen |
| ihr | ließt |
| sie / Sie | ließen |
Er ließ die Tür offen und ging.
He left the door open and walked off.
Sie ließen sich Zeit mit der Entscheidung.
They took their time with the decision. (sich Zeit lassen — to take one's time)
Perfekt (present perfect)
Here lassen has two Perfekt forms, and which one you use depends on the structure of the sentence:
- Standalone lassen ("to leave [something somewhere]") uses the normal participle gelassen: Ich habe den Schlüssel zu Hause gelassen.
- As a causative or permission verb governing another infinitive, lassen forms a double infinitive (Ersatzinfinitiv): the participle is replaced by the bare infinitive lassen, which goes to the very end: Ich habe das Auto reparieren lassen — never …repariert gelassen.
| Person | Standalone (gelassen) | Causative (double infinitive) |
|---|---|---|
| ich | habe gelassen | habe … lassen |
| du | hast gelassen | hast … lassen |
| er / sie / es | hat gelassen | hat … lassen |
| wir | haben gelassen | haben … lassen |
| ihr | habt gelassen | habt … lassen |
| sie / Sie | haben gelassen | haben … lassen |
Ich habe mein Handy im Auto gelassen.
I left my phone in the car. (standalone — real participle gelassen)
Wir haben uns die Haare schneiden lassen.
We got our hair cut. (causative — double infinitive: schneiden lassen at the end)
The causative: "to have something done"
This is the heart of lassen. With a bare infinitive (no zu), lassen means either let / allow or have / get something done by someone else. German uses one verb where English needs three ("let," "have," "get/make").
Ich lasse mir die Pizza nach Hause liefern.
I'm having the pizza delivered to my house. (causative — I'm not delivering it myself)
Der Chef lässt uns heute früher gehen.
The boss is letting us leave early today. (permission sense)
Note that the bare infinitive — liefern, gehen — appears without zu. This is unusual; most German "verb + infinitive" patterns require zu. Lassen belongs to the small club of verbs (with the modals, sehen, hören, gehen and a few others) that take the bare infinitive. See bare infinitive.
The sich lassen passive
sich lassen + infinitive expresses possibility in a passive sense — roughly English "can be …ed." It is a stylish, common alternative to a full werden-passive with können.
Das Problem lässt sich leicht lösen.
The problem can be solved easily. (= Das Problem kann leicht gelöst werden, but lighter and more idiomatic)
Diese Tür lässt sich nicht abschließen.
This door can't be locked. (something is structurally wrong with it)
Compare this with the man-construction and the full passive on man vs passive.
Plusquamperfekt, Futur I, Konjunktiv II
| Person | Plusquamperfekt (standalone) | Futur I | Konjunktiv II |
|---|---|---|---|
| ich | hatte gelassen | werde lassen | ließe |
| du | hattest gelassen | wirst lassen | ließest |
| er / sie / es | hatte gelassen | wird lassen | ließe |
| wir | hatten gelassen | werden lassen | ließen |
| ihr | hattet gelassen | werdet lassen | ließet |
| sie / Sie | hatten gelassen | werden lassen | ließen |
The Konjunktiv II ließe (Präteritum stem ließ- + umlaut-less ending, since ie cannot take an umlaut) is common in polite or hypothetical statements.
An deiner Stelle ließe ich das einen Fachmann machen.
If I were you, I'd have a specialist do that. (Konjunktiv II ließe in the causative)
Imperativ (commands)
No a → ä change in the imperative. The du-form is Lass! — one of the highest-frequency commands in spoken German.
| Addressee | Form |
|---|---|
| du | Lass! |
| ihr | Lasst! |
| Sie | Lassen Sie! |
Lass uns gehen!
Let's go! (the standard German equivalent of English 'let's' — lass + uns)
Common idioms and fixed expressions
| Expression | English |
|---|---|
| Lass mich in Ruhe. | Leave me alone. (informal) |
| Lass uns ... | Let's ... (suggestion) |
| sich Zeit lassen | to take one's time |
| etwas sein lassen | to drop / stop doing something (informal) |
| Das lässt sich machen. | That can be done / arranged. |
Lass das bitte sein, das nervt.
Please stop that, it's annoying. (informal; etwas sein lassen = quit doing it)
Common Mistakes
❌ Ich habe das Auto reparieren gelassen.
Incorrect — when lassen governs an infinitive, the Perfekt uses the double infinitive, not gelassen.
✅ Ich habe das Auto reparieren lassen.
I had the car repaired.
❌ Ich lasse die Pizza zu liefern.
Incorrect — lassen takes a bare infinitive, never zu.
✅ Ich lasse die Pizza liefern.
I'm having the pizza delivered.
❌ Du lasst mich nie ausreden.
Incorrect du-form — the du-form is lässt (with umlaut); lasst is the ihr-form/imperative.
✅ Du lässt mich nie ausreden.
You never let me finish.
❌ Das Problem kann sich leicht lösen.
Incorrect — the possibility-passive is sich lassen, not kann sich; use 'lässt sich lösen'.
✅ Das Problem lässt sich leicht lösen.
The problem can be solved easily.
❌ Ich habe meinen Schlüssel zu Hause geließen.
Incorrect — the standalone participle is gelassen; geließen does not exist.
✅ Ich habe meinen Schlüssel zu Hause gelassen.
I left my key at home.
Key Takeaways
- Principal parts: lassen – ließ – hat gelassen (Perfekt with haben); watch ss (present lässt) vs ß (past ließ).
- Present a → ä: lasse, lässt, lässt — the du- and er-forms are identical.
- Two Perfekts: standalone gelassen ("leave"), but double infinitive (…machen lassen) whenever lassen governs another verb.
- Lassen
- bare infinitive = causative ("have something done") or permission ("let").
- sich lassen
- infinitive = an idiomatic possibility-passive ("can be …ed").
- Lass uns … is how German says "let's."
Now practice German
Reading grammar gets you part of the way. The exercises are where it sticks — free, no signup needed.
Start learning German→Related Topics
- lassen: let, have done, and leaveB2 — The versatile verb lassen — permissive 'let', causative 'have something done', the reflexive sich lassen passive, and standalone 'leave/stop' — plus its double-infinitive Perfekt.
- The Bare Infinitive (without zu)B1 — The small set of verbs — modals, perception verbs, lassen, and motion verbs — that take a plain infinitive with no zu, and the double-infinitive Perfekt they trigger.
- The Perfekt of Modals: The Double InfinitiveB2 — Why modal verbs (and lassen, sehen, hören) form their Perfekt with a substitute infinitive instead of a participle, and why the auxiliary jumps forward in subordinate clauses.
- man vs the PassiveB2 — When to use the indefinite pronoun man (one/you/they + active verb) versus the werden-passive to express agentless or general actions — and why natural German uses far fewer passives than English.
- bleiben: Full Conjugation and UsageA1 — Complete conjugation of bleiben 'to stay / to remain' across every tense and mood, with its ei-ie-ie ablaut, its copula nominative complement, and why it takes sein in the Perfekt despite no motion.
- Present Tense: Strong Verbs with a to ä, au to äu, o to öA2 — How strong verbs add an umlaut (a to ä, au to äu, o to ö) in the du and er/sie/es forms only.