Special features of the modal verbs

CA111

Modal verbs dürfen, können, mögen, müssen, sollen and wollen govern the infinitive of a full verb and can have no additional complements (e.g. an object). The infinitive that is connected to a modal verb is not preceded by the word zu.

Examples	complement		case governed by the full verb
Ich kann dir nicht helfen.	dir	= dative object	helfen + dative
Peter will seine Oma besuchen.	seine Oma	= accusative object	besuchen + accusative

Modal verbs can be combined with other modal verbs.

Example

Du musst Deutsch können.

CA111A

A modal verb can be connected with an infinitive only if the subject of the modal verb is the subject of the infinitive.

Examples	subject of the modal verb	subject of the infinitive
Ich kann dir nicht helfen.	ich	ich
Peter will seine Oma besuchen.	Peter	Peter

CA111B

Modal verbs can also function as full verbs; in this case, they are not connected to an infinitive but to adverbial phrases that denote direction (same for all modal verbs) or to an accusative object (modal verbs wollen, mögen, ich möchte and können). These sentences are usually elliptical and the infinitive is not mentioned, because its meaning derives from context.

Examples	complement
Ich muss hin.	adverbial denoting direction
Sie will in die Stadt.	phrase denoting direction
Lisa möchte noch ein Stück Pizza.	accusative object
Ich kann Deutsch.	accusative object

CA111C

Modal verbs wollen and ich möchte can govern a dass-clause. In this case, the subject of wollen / ich möchte is not the same as the subject of the dass-clause. Dass-clauses with passive voice or modal verb structures are the exception to this rule.

Examples	subject of the modal verb	subject of the dass-clause
Ich will, dass du mir die Wahrheit sagst.	ich	du
Sie möchte, dass alle zur Party kommen.	sie	alle

CA111D

Modal verbs form the present perfect and the past perfect tenses with the auxiliary verb haben + infinitive, instead of the past participle (Partizip II).

Examples

Ich habe sofort nach Haus gehen müssen.

However, when modal verbs function as full verbs (i.e not connected to an infinitive), they form the present perfect and the past perfect with the past participle (Partizip II).

Examples

Ich habe sofort nach Haus gemusst.

CA111E

Furthermore, modal verbs do not:

1. form the imperative mood

2. form the passive voice. However, they can govern a passive infinitive.

Examples

Das Haus muss renoviert werden.