Doctoral degrees represent the highest level of academic achievement, typically requiring at least three years of study after earning the bachelor's or master's degree. Some doctorates, however, are honorary, meaning that the recipients don't have to complete an academic program. The two types of earned doctorates are professional doctorates, which demonstrate mastery in the skills necessary for a specific career, and research doctorates, which focus on academics and original research.

Honorary Degrees

Honorary doctorates, called "honoris causa" in Latin, go to recipients that a university wishes to honor for special accomplishments. This type of doctorate doesn't qualify the recipient for a job, but it provides recognition for what he's already done, typically over a long career. Although each university sets its own standards for honorary degrees, the usual qualifications include contributions to the arts, sciences, scholarship or public service. For example, Harvard University awarded a Doctor of Laws to Oprah Winfrey in 2013, and it awarded the same degree to former President George H.W. Bush in 2014.

Health Care Degrees

A large category of professional doctorates prepare graduates for health care careers. In addition to the Doctor of Medicine and Doctor of Dental Surgery degrees, other health-related doctorates include the Doctor of Optometry, Doctor of Ophthalmology, Doctor of Physical Therapy, Doctor of Chiropractic, Doctor of Pharmacy and Doctor of Veterinary Medicine. These degrees typically require three to four years of study after the bachelor's degree, including coursework, labs and supervised clinical practice or internships. The degrees alone aren't sufficient to begin a career, however, because graduates must fulfill licensing requirements, including passing exams.

Other Professional Degrees

Other professional doctorates take approximately three years of full-time study after the bachelor's is earned. For example, the professional Doctor of Jurisprudence, or J.D. degree, takes three years and qualifies the holder to take state bar exams to practice law. Some professional doctorates aren't required for entry-level work but prepare professionals for advancement. For example, an education doctorate, or Ed.D., emphasizes practical applications of educational theory and prepares educators for administrative roles in schools and colleges. Similarly, the professional Doctor of Engineering degree teaches engineers the skills necessary for administrative positions such as project manager.

Research Doctorates

A research doctorate prepares the scholar to teach in a college or university or conduct independent research. The requirements include coursework, comprehensive exams, original research and the preparation and defense of a thesis. The typical degree is the Doctor of Philosophy, available in a variety of majors in the humanities, sciences and engineering. Some programs begin after the bachelor's, while others follow a master's or professional degree. A Ph.D. typically takes seven years or more after the bachelor's, according to the American Graduate Education website. Universities also grant many other research degrees that are equivalent to the Ph.D., including the Doctor of Arts, Doctor of Music and Doctor of Science.