Genitive Case: Possessive 's (Explicado Fácil y Rápido)
In grammar, the genitive ; also called the second case, is the grammatical case that marks a word, usually a noun, as modifying another word, also usually a noun. A genitive can serve purposes other than indicating relationships other than one noun's relationship to another noun; for example, some verbs may feature arguments in the genitive case, and it may also have adverbial uses.