A group of new Ph.D graduates with their professors
A Doctor of Philosophy (PhD,Ph.D., or DPhil; LatinPhilosophiae doctor or Doctor philosophiae) is the highest academic degree awarded by universities in most countries. PhDs are awarded for programs across the whole breadth of academic fields. As an earned research degree, those studying for this qualification are usually not only required to demonstrate subject-matter expertise and mastery by examination, they are also often asked to make a new scholarly contribution to a particular area of knowledge through their own original research. The completion of a PhD is often a requirement for employment as a university professor, researcher, or scientist in many fields. Individuals who have earned a Doctor of Philosophy degree may, in many jurisdictions, use the title Doctor (often abbreviated "Dr" or "Dr.") or, in non-English speaking countries, variants such as "Dr. phil." with their name, although the proper etiquette associated with this usage may also be subject to the professional ethics of their own scholarly field, culture, or society. Those who teach at universities or work in academic, educational, or research fields are usually addressed by this title "professionally and socially in a salutation or conversation." Additionally, holders of this degree may use post-nominal letters such as "Ph.D.", "PhD", or "DPhil" (depending on the awarding institution). However, they should never list both "Dr." and "Ph.D." with their name in reference to the same academic qualification, as this is considered redundant, possibly misleading, and in poor taste.
The specific requirements to earn a PhD degree vary considerably according to the country, institution, and time period, from entry-level research degrees to higher doctorates. During the studies that lead to the degree, the student is called a doctoral student or PhD student; a student who has completed all of their coursework and comprehensive examinations and is working on their thesis/dissertation is sometimes known as a doctoral candidate or PhD candidate (see: all but dissertation). A student attaining this level may be granted a Candidate of Philosophy degree at some institutions, or may be granted a master's degree en route to the doctoral degree. Sometimes this status is also colloquially known as "Ph.D. ABD", meaning "All But Dissertation."
In the context of the Doctor of Philosophy and other similarly titled degrees, the term "philosophy" does not refer to the field or academic discipline of philosophy, but is used in a broader sense in accordance with its original Greek meaning, which is "love of wisdom". In most of Europe, all fields (history, philosophy, social sciences, mathematics, and natural philosophy/sciences) other than theology, law, and medicine (the so-called professional, vocational, or technical curriculum) were traditionally known as philosophy, and in Germany and elsewhere in Europe the basic faculty of liberal arts was known as the "faculty of philosophy".
The degree is abbreviated PhD (sometimes Ph.D. in North America), from the Latin Philosophiae Doctor, pronounced as three separate letters (iː/). The abbreviation DPhil, from the English 'Doctor of Philosophy', is used by a small number of British and Commonwealth universities, including Oxford and formerly York and Sussex, as the abbreviation for degrees from those institutions.