"Saxon genitive" is the traditional term used for the ’s (apostrophe-s) word-ending in the English language. The term is now infrequently used by linguists who argue that ’s represents a possessive case, not a genitive. For further information about usage, see apostrophe.
In older English there are examples of it being spelt as "his" as a folk-etymology, e.g. "St. James his park", see his genitive.
Many English writers have adopted the nonstandard usage (even in formal writing) of adding only an apostrophe for the singular possessive of a noun ending in "s". Pronouns do not combine with ’s to form possessives; there are a range of possessive pronouns used instead.
In Old English, nouns declined according to grammatical gender. The modern Saxon genitive is derived from the strong masculine and neuter genitive case of Old English. The plural forms are a relatively modern innovation, and are not derived from Old English.
The term "Saxon genitive" is in analogy to the genitive in classical Latin.
Many contend that ’s now functions as a clitic rather than a case ending: it gets separated from its noun in modern usages such as "the King of Spain’s hat", which in theory is ambiguous between "the hat of the king of Spain" (intended meaning) or "the king of the hat of Spain". (Older usage had "the king’s hat of Spain" or, rarely, "Spain's king's hat"; an example in literature is "The King's daughter of Noroway" in The Ballad of Sir Patrick Spens.)
