German AcI: Verbs of Command and Perception (lassen, sehen, hören)
Grammar Rule in 30 Seconds
Use the AcI construction to describe an action being performed by someone else that you perceive or command.
- Use perception verbs (sehen, hören, fühlen) + Accusative Object + Infinitive: 'Ich sehe {den|m} Mann kommen.'
- Use 'lassen' for causative/command: 'Ich lasse {das|n} Auto reparieren.'
- The infinitive always stays at the very end of the clause.
Overview
At the C2 level, a mastery of grammatical nuance distinguishes true fluency. One such structure, the Accusativus cum Infinitivo (AcI), or Accusative with Infinitive, offers an elegant and concise way to express causation, permission, or direct perception in German. Originating from Latin, the AcI construction provides an alternative to more cumbersome subordinate clauses, lending an immediate and dynamic quality to your prose and speech.
While its underlying principle involves a direct object performing the action of an infinitive, its precise application with verbs like lassen (to let/allow/have done), sehen (to see), and hören (to hear) reveals layers of meaning and stylistic choice. Understanding the AcI allows you to move beyond simply conveying information to shaping how that information is perceived, making your German sound considerably more authentic and sophisticated.
This construction is not merely a syntactic trick; it reflects a specific cognitive framing of an event where the action is directly observed or caused, rather than merely reported. You will encounter the AcI extensively in literature, formal discourse, journalism, and even in nuanced everyday communication where brevity and impact are valued. Mastering its usage is a hallmark of C2 proficiency, enabling you to articulate complex ideas with precision and idiomatic grace.
The AcI allows for a streamlined presentation of events, focusing on the direct experience of seeing, hearing, or causing an action, bypassing the indirectness of a dass-clause. For instance, comparing Ich sehe, dass er kommt. (I see that he is coming – a reported fact) with Ich sehe ihn kommen. (I see him coming – a direct perception) illustrates this fundamental difference in experiential immediacy.
How This Grammar Works
Accusativus cum Infinitivo label precisely describes its components: an accusative noun or pronoun (Accusativus) accompanied by an infinitive (Infinitivo). Unlike typical subordinate clauses introduced by dass, which often present an action as a fact or report, the AcI conveys a direct, unmediated experience or causation of the action described by the infinitive.Ich höre das Kind lachen. Here, höre is the main verb, das Kind is the accusative object, and lachen is the bare infinitive. Syntactically, das Kind functions as the direct object of hören. Semantically, however, das Kind is the entity performing the action of lachen.hören) establishes the perception, and the accusative object is the perceived agent of the infinitive's action. The absence of zu before the infinitive is a defining characteristic, distinguishing it from zu-infinitive constructions that convey purpose or obligation.- Verbs of Perception (Perzeptionsverben):
sehen(to see),hören(to hear),fühlen(to feel),spüren(to sense/feel). These verbs express direct sensory input, implying that the observer is witnessing the action firsthand. For example,Sie sieht die Blätter fallen.(She sees the leaves fall.) - Verbs of Causation/Permission (Kausativverben/Permissivverben): Primarily
lassen(to let, to allow, to have something done). This verb signifies actively causing or permitting an action by another party or having an action performed. For instance,Er lässt den Mechaniker das Auto reparieren.(He has the mechanic repair the car / He lets the mechanic repair the car.)
dass-clauses, with their more detached, report-like quality, cannot convey.Formation Pattern
sehen, hören, fühlen, spüren) or causation/permission (lassen). It must be correctly conjugated according to the main clause subject and tense.
zu.
Ich | lasse | den Hund | laufen | Ich lasse den Hund laufen. (I let the dog run.) |
Du | lässt | ihn | arbeiten | Du lässt ihn arbeiten. (You let him work.) |
Wir | sehen | die Kinder | spielen | Wir sehen die Kinder spielen. (We see the children playing.) |
Ihr | hört | einen Vogel | singen | Ihr hört einen Vogel singen. (You hear a bird singing.) |
Sie | fühlte | ihr Herz | schlagen | Sie fühlte ihr Herz schlagen. (She felt her heart beat.) |
Ich sehe ihn sich rasieren. (I see him shaving himself.) The sich refers to ihn.
Ich höre die Tür aufgehen. (I hear the door open.) Here, aufgehen remains intact.
haben or sein) will be conjugated. However, with lassen, sehen, and hören in combination with an infinitive, the Ersatzinfinitiv (replacement infinitive) rule applies. Instead of the past participle (gelassen, gesehen, gehört), the infinitive form of the main verb is used alongside the infinitive of the action verb. Example: Ich habe ihn kommen sehen. (I have seen him come.) Not Ich habe ihn kommen gesehen. and definitely not Ich habe ihn kommen gesehen gehabt. This is a common C2-level subtlety.
When To Use It
dass-clauses or other constructions cannot replicate with the same immediacy.lassen (Causative/Permissive):lassen is arguably the most versatile of the AcI verbs, capable of expressing both permission and causation. Its meaning often depends on context, but the AcI structure consistently implies that the accusative object is the agent or recipient of the infinitive's action.- Permission/Allowance: To permit or allow someone or something to do something. The accusative object is the one receiving permission.
Die Eltern lassen die Kinder draußen spielen.(The parents let the children play outside.)Lass mich das erklären.(Let me explain that.) This is a common phrase in both formal and informal settings, demonstrating its utility.- Causation/Having Something Done: To arrange for something to be done, often by someone else, or to cause an event. This meaning often takes on a semi-passive connotation, where the subject causes the action without necessarily performing it directly. The agent performing the action might be implied or explicitly stated.
Ich lasse mir die Haare schneiden.(I have my hair cut.) – Here, the barber is the implied agent.Er lässt das Problem vom Team lösen.(He has the problem solved by the team.) – The team is the explicit agent.- Reflexive
sich lassen: Whenlassenis used reflexively, it often indicates possibility or feasibility, translating to
AcI Structure
| Subject | Main Verb | Accusative Object | Infinitive |
|---|---|---|---|
|
Ich
|
sehe
|
{den|m} Mann
|
kommen
|
|
Du
|
hörst
|
{die|f} Frau
|
singen
|
|
Er
|
lässt
|
{das|n} Kind
|
spielen
|
|
Wir
|
fühlen
|
{den|m} Boden
|
beben
|
|
Sie
|
lassen
|
{die|f} Tür
|
offenstehen
|
|
Ihr
|
seht
|
{den|m} Hund
|
laufen
|
Meanings
The AcI construction allows a speaker to link a perception or a causative action directly to the action performed by another entity.
Sensory Perception
Reporting what one perceives through the senses.
“Ich sehe {den|m} Hund rennen.”
“Sie hört {die|f} Musik spielen.”
Causative/Command
Causing someone else to perform an action (using 'lassen').
“Ich lasse {das|n} Fahrrad reparieren.”
“Er lässt {die|f} Kinder spielen.”
Reference Table
| Form | Structure | Example |
|---|---|---|
|
Affirmative
|
Subj + Verb + AccObj + Inf
|
Ich sehe {den|m} Jungen rennen.
|
|
Negative
|
Subj + Verb + AccObj + nicht + Inf
|
Ich sehe {den|m} Jungen nicht rennen.
|
|
Question
|
Verb + Subj + AccObj + Inf?
|
Siehst du {den|m} Jungen rennen?
|
|
Causative
|
Subj + lassen + AccObj + Inf
|
Ich lasse {das|n} Auto reparieren.
|
|
Past (Perfekt)
|
Subj + haben + AccObj + Inf + gesehen
|
Ich habe {den|m} Jungen rennen gesehen.
|
|
Reflexive
|
Subj + lassen + sich + Inf
|
Ich lasse mich nicht stören.
|
Formality Spectrum
Ich lasse {das|n} Fahrzeug instand setzen. (Service)
Ich lasse {das|n} Auto reparieren. (Service)
Ich lass {die|f} Karre machen. (Service)
Ich lass {die|f} Karre checken. (Service)
AcI Components
Verbs
- sehen to see
- hören to hear
- lassen to let
Object
- Akkusativ Accusative case
Action
- Infinitiv Infinitive form
Examples by Level
Ich sehe {den|m} Jungen.
I see the boy.
Ich höre {die|f} Musik.
I hear the music.
Ich sehe {den|m} Hund.
I see the dog.
Ich lasse {das|n} Buch hier.
I leave the book here.
Ich sehe {den|m} Hund rennen.
I see the dog running.
Ich höre {die|f} Vögel singen.
I hear the birds singing.
Ich lasse {das|n} Auto waschen.
I am having the car washed.
Siehst du {den|m} Mann kommen?
Do you see the man coming?
Ich lasse {die|f} Kinder im Garten spielen.
I let the children play in the garden.
Wir hörten {den|m} Regen gegen {das|n} Fenster klopfen.
We heard the rain tapping against the window.
Er lässt {die|f} Haare schneiden.
He is getting his hair cut.
Ich sehe {die|f} Sonne untergehen.
I see the sun setting.
Ich lasse {den|m} Techniker {das|n} Problem lösen.
I am having the technician solve the problem.
Man kann {die|f} Veränderung spüren.
One can feel the change.
Sie ließ {den|m} Brief auf {dem|m} Tisch liegen.
She left the letter lying on the table.
Ich habe {den|m} Zug abfahren sehen.
I saw the train depart.
Ich lasse mich nicht von {der|f} Situation einschüchtern.
I won't let myself be intimidated by the situation.
Er ließ {die|f} Nachricht unkommentiert.
He left the message uncommented.
Man hört {die|f} Wellen gegen {die|f} Klippen schlagen.
One hears the waves hitting the cliffs.
Ich lasse {die|f} Arbeit von {einem|m} Experten erledigen.
I am having the work done by an expert.
Er ließ {die|f} Maske fallen.
He let his mask fall (revealed his true self).
Man sah {den|m} König {das|n} Land verlassen.
One saw the king leaving the country.
Sie ließ {die|f} Gelegenheit ungenutzt verstreichen.
She let the opportunity pass by unused.
Ich höre {die|f} Glocken {die|f} Stunde schlagen.
I hear the bells striking the hour.
Easily Confused
Learners often use 'dass' clauses when AcI is more concise.
Both use the same verb.
Learners use the past participle instead of the infinitive.
Common Mistakes
Ich sehe {der|m} Mann kommen.
Ich sehe {den|m} Mann kommen.
Ich sehe {den|m} Mann kommt.
Ich sehe {den|m} Mann kommen.
Ich sehe kommen {den|m} Mann.
Ich sehe {den|m} Mann kommen.
Ich sehe {den|m} Mann zu kommen.
Ich sehe {den|m} Mann kommen.
Ich lasse {das|n} Auto repariert.
Ich lasse {das|n} Auto reparieren.
Ich höre, dass {die|f} Vögel singen.
Ich höre {die|f} Vögel singen.
Ich lasse {den|m} Mechaniker hat {das|n} Auto repariert.
Ich lasse {das|n} Auto reparieren.
Ich habe {den|m} Mann kommen gesehen.
Ich habe {den|m} Mann kommen sehen.
Ich lasse {mich|refl} nicht ärgern.
Ich lasse mich nicht ärgern.
Ich lasse {das|n} Haus bauen.
Ich lasse {das|n} Haus bauen.
Er ließ {die|f} Chance verstreichen.
Er ließ {die|f} Chance verstreichen.
Ich lasse {die|f} Arbeit erledigen von {dem|m} Experten.
Ich lasse {die|f} Arbeit von {einem|m} Experten erledigen.
Sie sah {den|m} Zug abfahren.
Sie sah {den|m} Zug abfahren.
Ich lasse {das|n} Kind spielen.
Ich lasse {das|n} Kind spielen.
Sentence Patterns
Ich sehe ___ ___.
Ich lasse ___ ___.
Ich habe ___ ___ gesehen.
Man kann ___ ___ spüren.
Real World Usage
Ich lasse meine Unterlagen prüfen.
Ich sehe {die|f} Welt sich verändern.
Ich hör {die|f} Nachbarn streiten.
Ich lasse {das|n} Gepäck im Hotel.
Ich lasse {das|n} Essen liefern.
Man sah {den|m} Präsidenten das Land verlassen.
Keep it simple
Watch the case
End position
Formal vs Informal
Smart Tips
Check if the first is a perception verb; if so, the second must be an infinitive.
Think of it as 'I am having it done'.
Use AcI to make your sentences more concise.
Remember the double infinitive rule.
Pronunciation
Infinitive stress
The infinitive at the end usually carries the main stress of the phrase.
Falling intonation
Ich sehe {den|m} Mann kommen. ↘
Declarative statement.
Memorize It
Mnemonic
See, Hear, Let — the Accusative is the pet, the Infinitive is the set.
Visual Association
Imagine a movie director (the subject) pointing at an actor (the accusative object) and telling them to perform an action (the infinitive). The director is the main verb, the actor is the object, and the action is the infinitive at the end.
Rhyme
See, hear, or let, the infinitive at the end you must set.
Story
I see the cat (accusative) sit (infinitive). I hear the dog (accusative) bark (infinitive). I let the bird (accusative) fly (infinitive).
Word Web
Challenge
Look out your window for 5 minutes and describe 3 things you see using the AcI structure.
Cultural Notes
AcI is standard in formal and professional settings.
Similar to Germany, but 'lassen' is often used in colloquial speech.
Very formal in writing, but spoken German uses it frequently.
Derived from Latin Accusativus cum Infinitivo.
Conversation Starters
Was lässt du gerade reparieren?
Wen hast du heute rennen sehen?
Was lässt du dir von anderen erledigen?
Welche Geräusche hörst du gerade?
Journal Prompts
Common Mistakes
Test Yourself
Ich sehe {den|m} Mann ___ (kommen).
Which is correct?
Find and fix the mistake:
Ich höre {die|f} Vögel singt.
Arrange the words in the correct order:
All words placed
Click words above to build the sentence
I see the dog running.
Answer starts with: Ich...
A: Was machst du? B: Ich lasse ___.
Ich / lassen / {die|f} / Haare / schneiden
Which are perception verbs?
Score: /8
Practice Exercises
8 exercisesIch sehe {den|m} Mann ___ (kommen).
Which is correct?
Find and fix the mistake:
Ich höre {die|f} Vögel singt.
sehen / ich / kommen / {den|m} / Mann
I see the dog running.
A: Was machst du? B: Ich lasse ___.
Ich / lassen / {die|f} / Haare / schneiden
Which are perception verbs?
Score: /8
Practice Bank
10 exerciseshöre / ich / singen / Nachbarn / {den|m} / .
I let him do the work.
Wir sahen {das|n} Flugzeug am Himmel ____.
Match these AcI trigger verbs:
Pick the high-level formal sentence:
Ich fühlte {das|n} Adrenalin in meinen Adern zu steigen.
Ich sah {den|m} Influencer live ____.
die Mutter / räumen / hieß / {den|m} Sohn / auf / .
How do you say it using AcI?
Select the correct causative use:
Score: /10
FAQ (8)
No, only with perception verbs and 'lassen'.
No, it remains in the base form.
It is used in all registers.
It's grammatically correct but less concise.
Yes, use 'haben' + infinitive + 'gesehen'.
Yes, very common.
Conjugating the infinitive.
Yes, e.g., 'Ich lasse mich nicht stören'.
Scaffolded Practice
1
2
3
4
Mastery Progress
Needs Practice
Improving
Strong
Mastered
In Other Languages
Ver + objeto + infinitivo
Spanish uses the personal 'a'.
Voir + objet + infinitif
French doesn't have the same case system.
~を見る (to see ~ doing)
Japanese is SOV, German is SVO/V2.
رأيتُ... يفعل
Arabic uses a conjugated verb instead of an infinitive.
看见...在...
Chinese has no verb conjugation or case.
See + object + infinitive
English doesn't have case declensions.
Learning Path
Prerequisites
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