The accusative case denotes the direct object or the object of an accusative or two-way preposition. The direct object is the noun that receives the action of the (transitive) verb. In other words, direct objects are those being “verbed” by the subject, for example:
The boy sees the book. (Subject – Verb – Direct Object)
The subject of the sentence (the one performing the action/verb) is the boy. The direct object is the one being “verbed,” in this case, “seen.” Thus, the book is the direct object. This particular verb is transitive, which means simply that its action “transfers” to a direct object.
There are also intransitive verbs, which have no direct object — for example, “The couple drives to Berlin.” In this sentence, Berlin cannot “be driven,” though one can drive to the city (“to the city” = prepositional phrase, which has an object of the preposition that is not equal to the direct object). In this way, “to drive” is an intransitive verb, because its action does not transfer to the city of Berlin itself — in the latter case, it would entail Berlin becoming a means of transportation to be used by the couple. Another example of an intransitive verb is “to go”: one can go somewhere (part of a prepositional phrase, e.g. to the store, to Europe), but the place is not “being gone” (i.e. it makes no sense to think of a fixed location moving to another place).
The accusative case also has 5 commonly-used prepositions that only take the accusative: durch, für, gegen, ohne, and um. These prepositions typically are followed by an article before their object (e.g. durch den Park, gegen den Baum), but sometimes an article is not necessary, as in the case of personal pronouns (e.g. ohne dich, für ihn). There are also 9 two-way prepositions that can take either the accusative or dative case.
There is very little change from the Nominative to the Accusative cases: only masculine nouns and their articles are affected. The definite article der and the indefinite and negative articles ein and kein change to den, einen, and keinen, respectively. Take a look at the table below:
Examples: Ich möchte den/einen/keinen Apfel.
Du isst die/eine/keine Birne.
Er hört das/ein/kein Auto.
Wir sehen die/—/keine Eltern.
The personal pronouns also change to some extent in the accusative case:
In addition to the articles and pronouns, there are 5 commonly used prepositions that always take the accusative case, as well as 9 that can be used with either the accusative or dative cases, depending on the context. They are:
Akkusativpräpositionen (accusative prepositions)
Wechselpräpositionen im Akkusativ (two-way prepositions in the accusative)
*Typically, “zwischen” is used with two or more objects (e.g. Er geht zwischen den Park und die Kirche.).
Two-way prepositions are often used in conjunction with a handful of verbs of location in the accusative:
stellen – to place (upright)
setzen – to set (oneself)
legen – to lay (down)
stecken – to place/stick inside
hängen – to hang (something)
These verbs of location take accusative when a subject is placing an object somewhere (e.g. Das Mädchen legt das Buch auf den Tisch. / The girl lays the book on the table.), whereas the dative case is used to describe a fixed or static location (e.g. Das Buch liegt auf dem Tisch. / The book lies/is lying on the table.).