Refers to a person who holds a doctoral degree, or the degree itself. Commonly used as a title (e.g., 田中博士) or suffix (e.g., 文学博士).
He earned his PhD last year.
Dr. Tanaka is an authority in this field.
Dr. Tanaka developed a new medicine.
He earned his PhD at the age of thirty.
He's known as the insect expert.
postdoctoral researcher; postdoc