The genitive form, which does not exist in modern English as an inflection, represents an of relationship, which may or may not be possessive; in other words, the possessive is a subset of genitive. For example, the genitive form "speed of the car" is equivalent to the possessive form "the car's speed". However, the genitive form "pack of dogs" is not the same as the possessive form "dogs' pack" (though it is the same as "dog pack", which is not possessive).