The highest degree/ that a student/ can earn/ is a doctorate. Some doctorates/ are professional degrees, as opposed to a degree/ based on research. Medical students, for example, receive an M.D., from the Latin term/ for "doctor of medicine." Future lawyers/ receive a J.D., for "juris" or "jurum" doctor, meaning a doctor/ of law or laws.

Someone/ with a PhD/ is a "doctor of philosophy." Many people/ earn a PhD, yet not many/ are philosophers. The name/ has survived/ since the Middle Ages/ when many areas of study/ were called/ philosophy.

Students/ can receive a PhD/ in engineering, social work, education, music, history/ and a lot of other areas. Requirements/ can differ/ from one university/ to another, and from one area of study/ to another. But the National Science Foundation says/ American doctoral education/ is organized/ around a research experience.

A PhD/ usually requires/ at least three years of full-time study/ after a bachelor's degree. Some people/ first get a master's degree, others do not.

PhD candidates/ must also pass special examinations/ and carry out original research. Students/ present their findings/ by writing a dissertation, a long paper/ that they have to defend/ before a group of experts.

Every year, the federal government/ collects information/ on research doctorates/ awarded in the United States. More than forty-three thousand students/ received a research doctorate/ in two thousand five, the most recent year/ reported.

Close to one-third of those doctorates/ went to foreign students/ in the United States/ on a temporary visa. The largest numbers/ came from China, South Korea, India, Taiwan/ and Canada. Most of them/ studied engineering, physical science/ or life science.

The University of Illinois/ awarded the largest number/ of doctorates/ to foreign students. The other universities/ in the top five/ were Purdue, Ohio State, Texas A&M and Pennsylvania State.