Final answer:
A physician who works under the supervision of a senior staff physician is called a Resident.
Step-by-step explanation:
A physician who works under the supervision of a senior staff physician is called a(n) Resident.
A resident is a qualified medical doctor who is undergoing further training in a specific medical specialty. They work in a hospital or medical center and are supervised by senior staff physicians.
Residency is a crucial step in a physician's training and typically lasts for several years, during which residents gain valuable clinical experience and further develop their medical skills.