Doctor of Philosophy

PhD, Ph.D., DPhil, or Doctor of Philosophy (philosophiae doctor or doctor philosophiae; Latin philosophiae doctor or doctor philosophiae) is the highest academic degree that may be conferred after completing a term of study. Dr.Phil. degrees are given out for programmes that span the whole spectrum of academic disciplines. In order to receive their PhD, students are needed to do original research that advances the frontiers of knowledge, which is often presented in the form of a thesis or dissertation, and to defend their findings before a panel of other professionals who are experts in the subject. Doctoral study is often required for positions such as university professor, researcher, or scientist in a variety of areas. The title Doctor (often abbreviated "Dr." or "Dr.") may be used by individuals who have earned a Doctor of Philosophy degree in many jurisdictions, though the proper etiquette associated with this usage may also be subject to the professional ethics of their own scholarly field, culture, or society, as well as the professional ethics of their own country. The title "Ph.D." is often used to greet those who teach at universities or work in academic, educational, or research sectors "both professionally and socially in a salutation or conversation." Alternatively, holders may use post-nominal letters such as "PhD.", "DPhil," or "PhD." (depending on the awarding institution). It is, however, deemed inappropriate to use both the title and the post-nominals at the same time in the same sentence.

According to the nation, institution, and historical period, precise criteria for earning a PhD degree might vary significantly, ranging from entry-level research degrees to higher doctorates and everything between. Doctoral students and PhD students are referred to as such during the course of their studies leading to the degree; students who have completed all coursework and comprehensive examinations and are currently working on their thesis or dissertation are referred to as doctoral candidates and PhD candidates, respectively, during this time (see: all but dissertation). A student who reaches this level may be awarded a Candidate of Philosophy degree at certain universities, or he or she may be awarded a master's degree as a stepping stone to a doctorate degree at other institutions. This position is sometimes referred to as "PhD ABD," which stands for "All But Dissertation" in colloquial language.