What is the formal forms of "you"?
Sie (always capitalized) is both singular and plural and is used in the Nominative (subject) Case and Accusative (Direct Object) Case. 'Sie' changes to Ihnen (always capitalized) in the Dative (Indirect Object) Case. In the Genitive (Possessive) Case "Sie' changes to Ihr and adds endings. The Genitive Case is not used often in modern spoken German.