Webster's Revised Unabridged Dictionary · 1913

A scholastic degree awarded for study beyond college; the Doctorate degree in Philosophy. In America it is usually based on at least 3 years graduate study and a dissertation; the doctorate is the highest degree awarded by a graduate school, and is awarded in other fields, such as Doctor of Arts. The Ph.D. is broadly applicable, as in most fields of science and technology; -- the term philosophy being derived from an earlier label for experimental science as Natural Philosophy.