[4.] An appositive agrees in case with the noun which it explains. [§ 81].
[5.] Adjectives agree with their nouns in gender, number, and case. [§ 65].
[6.] A predicate adjective completing a complementary infinitive agrees in gender, number, and case with the subject of the main verb. [§ 215. a].
[7.] A relative pronoun must agree with its antecedent in gender and number; but its case is determined by the way it is used in its own clause. [§ 224].
Prepositions
[8.] A noun governed by a preposition must be in the accusative or ablative case. [§ 52].
Genitive Case
[9.] The word denoting the owner or possessor of something is in the genitive and answers the question Whose? [§ 38].
[10.] The possessive genitive often stands in the predicate, especially after the forms of sum, and is then called the predicate genitive. [§ 409].
[11.] Words denoting a part are often used with the genitive of the whole, known as the partitive genitive. [§ 331].