The master's degree, while still an advanced degree, is ranked at a lower level than the Ph.D. A master's degree is usually a prerequisite to beginning a Ph.D. program. The Ph.D. is considered a terminal degree; you can't study at a higher level than that. Just as undergraduate level courses help prepare students for graduate work, master's level courses help prepare students for Ph.D. work.
A master's degree generally takes two years to complete and a Ph.D. takes five years to complete. However, depending on the program, a master's degree may take as short as one year in duration or as long as three years, and a Ph.D. may take as short as four years or as long as ten years. As a general rule, humanities degrees take longer than more technical-oriented degrees.
The Ph.D. program is normally only studied after completion of a master's degree, but some joint master's/Ph.D. programs allow students to complete coursework for a master's degree and Ph.D. in a total of seven years.
A master's degree is a specialized degree that takes an in-depth look at a subject, but the Ph.D. requires thorough and exhaustive understanding of a topic. For this reason, Ph.D. holders are considered to be experts in their fields, while master's degree holders are not.
Advanced degrees consist of both coursework and research. Students are required to take a certain number of required and elective courses as well as perform original research, culminating in the thesis for master's degree students and the doctoral dissertation for PhD students. Yet, the PhD is more research oriented than the master's degree and requires a more advanced understanding of the topic.
Master's degree and Ph.D. holders are not equally qualified and considered when it comes to teaching in post-secondary institutions. Teachers at U.S. universities and four-year colleges are required to hold a Ph.D. On the other hand, the minimum requirement for teachers at two-year colleges is a master's degree. In practice, master's degree holders make up the majority of teachers at two-year colleges in the United States typically, but Ph.D. holders are preferred.