Cases show the grammatical role of a word in a sentence and connect form with function. The nominative marks the subject, predicate noun and the form of address; the accusative marks usually the direct object as well as some destination and time expressions; the dative marks the indirect object and the recipient; and the genitive marks possession as well as attributive relationships. The exact choice of case often depends on verbs, prepositions and sentence function, therefore looking at sentence structure is decisive. For the basic functions, the overviews for Nominative, Accusative, Dative, and Genitive.

Definite articles mark the case directly and differ according to gender and number. In the nominative and accusative there are overlaps in several forms, especially for feminine and plural, while the dative and genitive mark stronger distinctions. The forms are important for reliable case assignment in the sentence and form the basis for many structures with Definite Articles.

Indefinite articles appear only in the singular and show clear case shifts especially in the masculine and neuter. In the feminine, the nominative and accusative are the same, while dative and genitive form their own forms. These forms are especially important when a new or not precisely specified referent is introduced, as in the overview of Indefinite Articles.

kein behaves like an article and refers to countable or substantive meanings, while the zero article stands with indefinite quantities, substances, names and some fixed expressions. As with other articles words, the form of kein depends on gender, number and case. For general article use, looking at Kasus is also helpful.

Personal pronouns carry case marking even without a determiner and thus show the grammatical function in the sentence particularly clearly. Some forms distinguish nominative and accusative strongly, others are identical in the nominative and accusative, and in genitive there are usually longer, rarer forms. The system is closely linked to the cases and complements the forms in Dative and Genitive.

Adjectives adjust their endings to the article status and to the case. With definite article there are usually weak endings, with indefinite article mixed endings, and without articles strong endings, because the adjective must carry the case information more strongly. This is especially visible in the nominative, accusative and dative, while genitive in attributive constructions requires its own forms and is often connected with Genitive.

Weak nouns, especially masculine personal designations like der Junge, take in many forms an added -en or -n. This declension appears mainly in the oblique cases and remains a fixed exception within the nominal system. It complements the regular articles and endings and is usually used consistently in written German.

Fixed prepositions govern their case independently of the sentence content and therefore must be learned as fixed word combinations. mit takes the dative, für takes the accusative, and trotz as well as aufgrund require the genitive, even though spoken language often replaces the genitive with von plus the dative. Regional and stylistic differences show up especially in that the genitive is more common in written German and less common in everyday life, while verbs and prepositions remain stable in their case binding. For spatial changes, pay attention to Wechselpräpositionen, and in everyday life the connection with Präpositionen helps.

Two-way prepositions connect two spatial perspectives with two different cases. The accusative shows direction or movement toward a destination, the dative shows location or position without movement. The main forms are on, onto, in, over, and under, and the case is determined by movement or location.

Cases order the sentence roles and make relationships between verbs, nouns, pronouns and prepositions visible. The nominative names the subject and its reference in the sentence, the accusative marks the direct object, the dative the recipient or affected party, and the genitive shows possession or close association. Articles, pronouns, adjective endings and nouns reflect these functions in their forms, while fixed prepositions and verb-bound constructions determine the case in advance.