C2 Infinitive Constructions 8 min read Medium

German AcI: Verbs of Command and Perception (lassen, sehen, hören)

Use the Accusative as the 'subject' for a final bare infinitive to create sleek, direct German sentences.

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.
Subject + Verb (Perception/Lassen) + Accusative Object + Infinitive

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

The core mechanism of the German AcI revolves around a main verb governing a construction where its direct object simultaneously acts as the logical subject of a bare infinitive. This 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.
Consider the sentence 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.
This dual role is crucial: the main verb (e.g., 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.
The AcI is predominantly used with specific categories of verbs:
  • 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(m) Mechaniker das Auto reparieren. (He has the mechanic repair the car / He lets the mechanic repair the car.)
The AcI structure provides a concise way to link a perception or a command to an action without creating a separate subordinate clause. This makes the sentence flow more smoothly and often emphasizes the directness of the interaction or observation. It inherently carries a sense of immediacy and direct involvement, which dass-clauses, with their more detached, report-like quality, cannot convey.
You are not reporting about an action; you are witnessing or instigating it.

Formation Pattern

1
Forming an AcI sentence involves a straightforward yet strict sequence of elements. Mastery lies in correctly identifying the main verb, ensuring the correct case for the object, and most importantly, using the bare infinitive. The pattern consistently follows: Main Clause Subject (Nominative) + Conjugated AcI-Trigger Verb + Accusative Object + Bare Infinitive (at the end).
2
Main Clause Subject: This is the entity performing the action of the AcI-trigger verb. It will always be in the Nominative case.
3
Conjugated AcI-Trigger Verb: This is the verb of perception (sehen, hören, fühlen, spüren) or causation/permission (lassen). It must be correctly conjugated according to the main clause subject and tense.
4
Accusative Object: This is the noun or pronoun that is both the direct object of the trigger verb and the logical subject of the action described by the infinitive. It must always be in the Accusative case.
5
Bare Infinitive: This is the second verb, placed at the very end of the clause. Crucially, it remains in its base, unconjugated infinitive form and never takes zu.
6
Here is a tabular representation of the common patterns:
7
| Main Verb Category | Main Clause Subject | AcI-Trigger Verb (conjugated) | Accusative Object | Bare Infinitive | Example Sentence |
8
| :----------------- | :------------------ | :---------------------------- | :---------------- | :-------------- | :------------------------------------------------------------------------------------------------------------------------------------ |
9
| Causative/Permissive | Ich | lasse | den(m) Hund | laufen | Ich lasse den(m) Hund laufen. (I let the dog run.) |
10
| | Du | lässt | ihn(m) | arbeiten | Du lässt ihn(m) arbeiten. (You let him work.) |
11
| Perception | Wir | sehen | die Kinder | spielen | Wir sehen die Kinder spielen. (We see the children playing.) |
12
| | Ihr | hört | einen Vogel | singen | Ihr hört einen Vogel singen. (You hear a bird singing.) |
13
| | Sie | fühlte | ihr(f) Herz | schlagen | Sie fühlte ihr(f) Herz schlagen. (She felt her heart beat.) |
14
Special Considerations:
15
Reflexive Verbs: If the infinitive is reflexive, the reflexive pronoun also appears in the accusative, typically after the AcI-trigger verb or the noun/pronoun object. Example: Ich sehe ihn(m) sich rasieren. (I see him shaving himself.) The sich refers to ihn.
16
Separable Prefixes: If the infinitive has a separable prefix, the prefix is not separated from the verb stem in the AcI construction, as it remains a single infinitive unit at the end. Example: Ich höre die Tür aufgehen. (I hear the door open.) Here, aufgehen remains intact.
17
Perfect Tenses: In perfect tenses, the main AcI-trigger verb will be in its past participle form, and the auxiliary verb (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(m) 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

The choice to employ an AcI construction is driven by both semantic precision and stylistic preference, particularly at the C2 level. It is not merely a grammatical variant but a tool to convey specific nuances that dass-clauses or other constructions cannot replicate with the same immediacy.
1. With 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(m/f) 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(m/f) 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: When lassen is 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.

1

Sensory Perception

Reporting what one perceives through the senses.

“Ich sehe {den|m} Hund rennen.”

“Sie hört {die|f} Musik spielen.”

2

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

Reference table for German AcI: Verbs of Command and Perception (lassen, sehen, hören)
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

Formal
Ich lasse {das|n} Fahrzeug instand setzen.

Ich lasse {das|n} Fahrzeug instand setzen. (Service)

Neutral
Ich lasse {das|n} Auto reparieren.

Ich lasse {das|n} Auto reparieren. (Service)

Informal
Ich lass {die|f} Karre machen.

Ich lass {die|f} Karre machen. (Service)

Slang
Ich lass {die|f} Karre checken.

Ich lass {die|f} Karre checken. (Service)

AcI Components

AcI Construction

Verbs

  • sehen to see
  • hören to hear
  • lassen to let

Object

  • Akkusativ Accusative case

Action

  • Infinitiv Infinitive form

Examples by Level

1

Ich sehe {den|m} Jungen.

I see the boy.

2

Ich höre {die|f} Musik.

I hear the music.

3

Ich sehe {den|m} Hund.

I see the dog.

4

Ich lasse {das|n} Buch hier.

I leave the book here.

1

Ich sehe {den|m} Hund rennen.

I see the dog running.

2

Ich höre {die|f} Vögel singen.

I hear the birds singing.

3

Ich lasse {das|n} Auto waschen.

I am having the car washed.

4

Siehst du {den|m} Mann kommen?

Do you see the man coming?

1

Ich lasse {die|f} Kinder im Garten spielen.

I let the children play in the garden.

2

Wir hörten {den|m} Regen gegen {das|n} Fenster klopfen.

We heard the rain tapping against the window.

3

Er lässt {die|f} Haare schneiden.

He is getting his hair cut.

4

Ich sehe {die|f} Sonne untergehen.

I see the sun setting.

1

Ich lasse {den|m} Techniker {das|n} Problem lösen.

I am having the technician solve the problem.

2

Man kann {die|f} Veränderung spüren.

One can feel the change.

3

Sie ließ {den|m} Brief auf {dem|m} Tisch liegen.

She left the letter lying on the table.

4

Ich habe {den|m} Zug abfahren sehen.

I saw the train depart.

1

Ich lasse mich nicht von {der|f} Situation einschüchtern.

I won't let myself be intimidated by the situation.

2

Er ließ {die|f} Nachricht unkommentiert.

He left the message uncommented.

3

Man hört {die|f} Wellen gegen {die|f} Klippen schlagen.

One hears the waves hitting the cliffs.

4

Ich lasse {die|f} Arbeit von {einem|m} Experten erledigen.

I am having the work done by an expert.

1

Er ließ {die|f} Maske fallen.

He let his mask fall (revealed his true self).

2

Man sah {den|m} König {das|n} Land verlassen.

One saw the king leaving the country.

3

Sie ließ {die|f} Gelegenheit ungenutzt verstreichen.

She let the opportunity pass by unused.

4

Ich höre {die|f} Glocken {die|f} Stunde schlagen.

I hear the bells striking the hour.

Easily Confused

German AcI: Verbs of Command and Perception (lassen, sehen, hören) vs Dass-Satz vs AcI

Learners often use 'dass' clauses when AcI is more concise.

German AcI: Verbs of Command and Perception (lassen, sehen, hören) vs Lassen (Causative) vs Lassen (Permission)

Both use the same verb.

German AcI: Verbs of Command and Perception (lassen, sehen, hören) vs Infinitive vs Participle

Learners use the past participle instead of the infinitive.

Common Mistakes

Ich sehe {der|m} Mann kommen.

Ich sehe {den|m} Mann kommen.

Wrong case used.

Ich sehe {den|m} Mann kommt.

Ich sehe {den|m} Mann kommen.

Conjugated the infinitive.

Ich sehe kommen {den|m} Mann.

Ich sehe {den|m} Mann kommen.

Wrong word order.

Ich sehe {den|m} Mann zu kommen.

Ich sehe {den|m} Mann kommen.

Added 'zu' unnecessarily.

Ich lasse {das|n} Auto repariert.

Ich lasse {das|n} Auto reparieren.

Used participle instead of infinitive.

Ich höre, dass {die|f} Vögel singen.

Ich höre {die|f} Vögel singen.

Unnecessary subordinate clause.

Ich lasse {den|m} Mechaniker hat {das|n} Auto repariert.

Ich lasse {das|n} Auto reparieren.

Over-complicating the structure.

Ich habe {den|m} Mann kommen gesehen.

Ich habe {den|m} Mann kommen sehen.

Double infinitive rule confusion.

Ich lasse {mich|refl} nicht ärgern.

Ich lasse mich nicht ärgern.

Reflexive pronoun placement.

Ich lasse {das|n} Haus bauen.

Ich lasse {das|n} Haus bauen.

Correct, but often confused with passive.

Er ließ {die|f} Chance verstreichen.

Er ließ {die|f} Chance verstreichen.

Correct, but often misused in complex sentences.

Ich lasse {die|f} Arbeit erledigen von {dem|m} Experten.

Ich lasse {die|f} Arbeit von {einem|m} Experten erledigen.

Wrong prepositional phrase placement.

Sie sah {den|m} Zug abfahren.

Sie sah {den|m} Zug abfahren.

Correct, but often confused with 'abgefahren'.

Ich lasse {das|n} Kind spielen.

Ich lasse {das|n} Kind spielen.

Correct, but often confused with 'dass' clauses.

Sentence Patterns

Ich sehe ___ ___.

Ich lasse ___ ___.

Ich habe ___ ___ gesehen.

Man kann ___ ___ spüren.

Real World Usage

Job Interview common

Ich lasse meine Unterlagen prüfen.

Social Media common

Ich sehe {die|f} Welt sich verändern.

Texting very common

Ich hör {die|f} Nachbarn streiten.

Travel occasional

Ich lasse {das|n} Gepäck im Hotel.

Food Delivery occasional

Ich lasse {das|n} Essen liefern.

News Report common

Man sah {den|m} Präsidenten das Land verlassen.

💡

Keep it simple

Don't overcomplicate the infinitive. It never changes.
⚠️

Watch the case

Always ensure the object is in the accusative.
🎯

End position

The infinitive is the anchor at the end of the sentence.
💬

Formal vs Informal

Use 'lassen' for services in formal settings.

Smart Tips

Check if the first is a perception verb; if so, the second must be an infinitive.

Ich sehe {den|m} Mann kommt. Ich sehe {den|m} Mann kommen.

Think of it as 'I am having it done'.

Ich lasse {das|n} Auto repariert. Ich lasse {das|n} Auto reparieren.

Use AcI to make your sentences more concise.

Ich sehe, dass {die|f} Sonne untergeht. Ich sehe {die|f} Sonne untergehen.

Remember the double infinitive rule.

Ich habe ihn kommen gesehen. Ich habe ihn kommen sehen.

Pronunciation

Ich sehe {den|m} Mann kom-men.

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

sehenhörenlassenfühlenspürenAkkusativInfinitiv

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

Describe your morning routine using 'lassen'.
Write about a busy street scene you observed.
Discuss a service you recently outsourced.
Reflect on a sensory experience in nature.

Common Mistakes

Incorrect

Correct


Incorrect

Correct


Incorrect

Correct


Incorrect

Correct

Test Yourself

Fill in the correct form.

Ich sehe {den|m} Mann ___ (kommen).

✓ Correct! ✗ Not quite. Correct answer: kommen
Infinitive is required.
Choose the correct sentence. Multiple Choice

Which is correct?

✓ Correct! ✗ Not quite. Correct answer: Ich lasse das Auto reparieren.
Causative uses infinitive.
Fix the error. Error Correction

Find and fix the mistake:

Ich höre {die|f} Vögel singt.

✓ Correct! ✗ Not quite. Correct answer: singen
Infinitive required.
Reorder the words. Sentence Reorder

Arrange the words in the correct order:

All words placed

Click words above to build the sentence

✓ Correct! ✗ Not quite. Correct answer: Ich sehe {den|m} Mann kommen.
Correct word order.
Translate to German. Translation

I see the dog running.

Answer starts with: Ich...

✓ Correct! ✗ Not quite. Correct answer: Ich sehe {den|m} Hund rennen.
Accusative case.
Complete the dialogue. Dialogue Completion

A: Was machst du? B: Ich lasse ___.

✓ Correct! ✗ Not quite. Correct answer: {das|n} Auto reparieren
Causative structure.
Build a sentence. Sentence Building

Ich / lassen / {die|f} / Haare / schneiden

✓ Correct! ✗ Not quite. Correct answer: Ich lasse {die|f} Haare schneiden.
Correct structure.
Sort the verbs. Grammar Sorting

Which are perception verbs?

✓ Correct! ✗ Not quite. Correct answer: sehen, hören, fühlen
These are the core perception verbs.

Score: /8

Practice Exercises

8 exercises
Fill in the correct form.

Ich sehe {den|m} Mann ___ (kommen).

✓ Correct! ✗ Not quite. Correct answer: kommen
Infinitive is required.
Choose the correct sentence. Multiple Choice

Which is correct?

✓ Correct! ✗ Not quite. Correct answer: Ich lasse das Auto reparieren.
Causative uses infinitive.
Fix the error. Error Correction

Find and fix the mistake:

Ich höre {die|f} Vögel singt.

✓ Correct! ✗ Not quite. Correct answer: singen
Infinitive required.
Reorder the words. Sentence Reorder

sehen / ich / kommen / {den|m} / Mann

✓ Correct! ✗ Not quite. Correct answer: Ich sehe {den|m} Mann kommen.
Correct word order.
Translate to German. Translation

I see the dog running.

✓ Correct! ✗ Not quite. Correct answer: Ich sehe {den|m} Hund rennen.
Accusative case.
Complete the dialogue. Dialogue Completion

A: Was machst du? B: Ich lasse ___.

✓ Correct! ✗ Not quite. Correct answer: {das|n} Auto reparieren
Causative structure.
Build a sentence. Sentence Building

Ich / lassen / {die|f} / Haare / schneiden

✓ Correct! ✗ Not quite. Correct answer: Ich lasse {die|f} Haare schneiden.
Correct structure.
Sort the verbs. Grammar Sorting

Which are perception verbs?

✓ Correct! ✗ Not quite. Correct answer: sehen, hören, fühlen
These are the core perception verbs.

Score: /8

Practice Bank

10 exercises
Put the words in the correct order. Sentence Reorder

höre / ich / singen / Nachbarn / {den|m} / .

✓ Correct! ✗ Not quite. Correct answer: Ich höre den Nachbarn singen.
Translate into German using an AcI. Translation

I let him do the work.

✓ Correct! ✗ Not quite. Correct answer: Ich lasse ihn die Arbeit machen.
Choose the correct infinitive ending. Fill in the Blank

Wir sahen {das|n} Flugzeug am Himmel ____.

✓ Correct! ✗ Not quite. Correct answer: verschwinden
Match the verb to its category. Match Pairs

Match these AcI trigger verbs:

✓ Correct! ✗ Not quite. Correct answer: lassen - Causative, sehen - Perception, heißen - Command
Which literary sentence uses AcI correctly? Multiple Choice

Pick the high-level formal sentence:

✓ Correct! ✗ Not quite. Correct answer: Sie hieß {den|m} Boten eintreten.
Correct the perception error. Error Correction

Ich fühlte {das|n} Adrenalin in meinen Adern zu steigen.

✓ Correct! ✗ Not quite. Correct answer: Ich fühlte das Adrenalin in meinen Adern steigen.
Complete the social media scenario. Fill in the Blank

Ich sah {den|m} Influencer live ____.

✓ Correct! ✗ Not quite. Correct answer: gehen
Order the elements of a command. Sentence Reorder

die Mutter / räumen / hieß / {den|m} Sohn / auf / .

✓ Correct! ✗ Not quite. Correct answer: Die Mutter hieß den Sohn aufräumen.
Translate 'I hear the music playing'. Translation

How do you say it using AcI?

✓ Correct! ✗ Not quite. Correct answer: Ich höre die Musik spielen.
Which sentence describes a service being performed? Multiple Choice

Select the correct causative use:

✓ Correct! ✗ Not quite. Correct answer: Ich lasse mir die Pizza liefern.

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

1

2

2

3

3

4

4

Mastery Progress

Needs Practice

Improving

Strong

Mastered

In Other Languages

Spanish high

Ver + objeto + infinitivo

Spanish uses the personal 'a'.

French high

Voir + objet + infinitif

French doesn't have the same case system.

Japanese low

~を見る (to see ~ doing)

Japanese is SOV, German is SVO/V2.

Arabic moderate

رأيتُ... يفعل

Arabic uses a conjugated verb instead of an infinitive.

Chinese low

看见...在...

Chinese has no verb conjugation or case.

English high

See + object + infinitive

English doesn't have case declensions.

Learning Path

Prerequisites

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