In general, a PhD program is a highly demanding research-oriented course that lasts for between three and five years. This length of time can vary depending on the subject area you choose to study, how well you are making progress with your research, and whether the individual is enrolled full-time or part-time in the program. Throughout this period, students conduct extensive research work, writing their dissertations and making original contributions to specific fields. Coursework, comprehensive examinations, and defense of the thesis form part of many PhD programs. A PhD is an indication of high expertise (therefore availing advanced career opportunities in academia, research, and other specialized sectors).