Nomenclature
The United States code does not refer to senior status in its body text, although the title of 28 U.S.C. § 371 is "Retirement on salary; retirement in senior status."
The term senior judge is defined by 28 U.S.C. § 294 to mean an inferior court judge who is in senior status.
Justices of the Supreme Court usually retire rather than taking senior status; a Justice having this status is thereafter referred to as a "retired justice." Senior judge is explicitly defined by 28 U.S.C. § 294, which also explicitly refers to the assignment of retired justices, making no mention of senior justice. When a circuit or district judge on senior status sits on an inferior court case, he or she is referred to as "Senior Judge" in the opinion, while a justice in the same position is referred to as "Justice, Retired."
Read more about this topic: Senior Status