The term that describes someone who has full social and civil rights is "sui juris." This Latin phrase translates to "of one's own right" and is used in legal contexts to indicate a person who possesses the capacity to make their own decisions and manage their affairs independently. Being sui juris denotes that an individual is not under any legal disability, and thus they can enter into contracts, manage property, and participate fully in society without restrictions that might be imposed due to guardianship or other legal limitations.
In contrast, other terms have distinct legal meanings. A ward refers to an individual who is under the protection of a guardian due to incapacity. A surety is a person who takes responsibility for another's performance of an obligation, often in a financial context. A trustee is an individual or organization that holds and manages the assets or property of another party, often under a legal trust agreement. These roles reflect varying levels of rights and capacities within legal structures, highlighting why "sui juris" is the most appropriate term for someone who enjoys full social and civil rights.