Use this second-person possessive pronoun when speaking directly to someone or to a group as in I love your hat. The archaic synonym thy can also be used in place of your as in I covet thy hat. Your is sometimes confused with its homophone you're, a contraction of you are.
Various spellings of your have existed in the language since Old English. At the turn of the seventeenth century thy, a now-outdated variant of your, was far more common than your, however by the 1620s, your was firmly established as the preferred second-person possessive pronoun in English.
Your can be used to express possession as in the phrase your jacket, which refers to the jacket belonging to you. It can also be used to more generally refer to any person. When a train conductor announces Doors open to your left, your is referring to each and every person on the train. Additionally, your can be used to indicate all the members of a group, as in Take your average high school student, for example. Your is not to be confused with you're, which is the contraction of you are.