Doctor, as a title, originates from the Latin word (gen.: doctoris) which means teacher. The word is originally an agentive noun of the verb docēre ('to teach'). It has been used as an honored academic title for over a millennium in Europe, where it dates back to the rise of the university. This use spread to the Americas, former European colonies, and is now prevalent in most of the world. Abbreviated "Dr" or "Dr.", it is used as a designation for a person who has obtained a doctorate-level degree. Doctorates may be research doctorates or professional doctorates. When addressing several people, both of whom holds a doctoral title, one may use the plural abbreviation "Drs." or in some languages, Dres., may be used, e.g., instead of Dr. Miller and Dr. Rubinstein: Drs. Miller and Rubinstein. When referring to relatives with the same surname the form "The Doctors Smith" can be used.
The origins of the doctorate lie in the Ijazah ("license to teach and issue legal opinions") in the medieval Islamic madrasahs from the 9th century. The foundations of the first universities in Europe were the glossators of the 11th century, which were schools of law. The first European university, that of Bologna, was founded as a school of law by four legal scholars in the 12th century who were students of the glossator school in that city. It is from this history that it is said that the first academic title of doctor was applied to scholars of law. The degree and title were not applied to scholars of other disciplines until the 13th century. And at the University of Bologna from its founding in the 12th century until the end of the 20th century the only degree conferred was the doctorate, usually earned after five years of intensive study after secondary school. The rising of the doctor of philosophy to its present level is a modern development.  At its origins, a doctorate was simply a qualification for a guild—that of teaching law.
Throughout much of the academic world, the term "doctor" refers to an individual who has earned a degree of Doctor of Philosophy, or Ph.D. (an abbreviation for the Latin Philosophiæ Doctor; or alternatively Doctor philosophiæ, D.Phil., originally from the Greek Διδάκτωρ Φιλοσοφίας, Didáktōr Philosophías, meaning Teacher of Philosophy), or other research doctorate such as the Doctor of Science, or Sc.D. (an abbreviation of the Latin Scientiae Doctor). Beyond academia and in the classical professions, such as medicine and law, professional doctorates emerged such as the Doctor of Medicine M.D. (an abbreviation of the Latin Medicinæ Doctor), Doctor of Osteopathic Medicine D.O., Bachelor of Medicine and Surgery MBBS, MBChB, MB, BCh, etc. (an abbreviation of the Latin Medicinae Baccalaureus et Baccalaureus Chirurgiae), BHMS (Bachelor of Homeopathic medicine and surgery), BAMS (Bachelor of ayurvedic medicine)
The first academic degrees were all law degrees, and the first law degrees were doctorates. The origins of the doctorate dates back to the ijazat attadris wa'l-ifttd ("license to teach and issue legal opinions") in the medieval Islamic Madrasahs that taught Islamic law since the 9th century. The foundations for the first European universities were the glossators of the 11th century, which were schools of law that taught Canon law and Roman law. The first European university, the University of Bologna, was founded as a school of law by four famous legal scholars in the 12th century who were students of the glossator school in Bologna. It is from this history that it is said that the first academic title of doctor applied to scholars of law. The degree and title were not applied to scholars of other disciplines until the 13th century. At the University of Bologna, from its founding in the 12th century until the end of the 20th century, the only degree conferred was the doctorate, usually earned after five years of intensive study after secondary school. The rising of the doctor of philosophy to its present level is a modern novelty. At its origins, a doctorate was simply a qualification for a guild—that of teaching law.
The earliest doctoral degrees (theology, law, and medicine) reflected the historical separation of all university study into these three fields. Over time the D.D. has gradually become less common and studies outside theology and medicine have become more common (such studies were then called "philosophy", but are now classified as sciences and humanities - however this usage survives in the degree of Doctor of Philosophy).
The Ph.D. was originally a degree granted by a university to learned individuals who had achieved the approval of their peers and who had demonstrated a long and productive career in the field of philosophy. The appellation of "Doctor" (from Latin: teacher) was usually awarded only when the individual was in middle age. It indicated a life dedicated to learning, to knowledge, and to the spread of knowledge.
The Ph.D. entered widespread use in the 19th century at the Friedrich Wilhelm University in Berlin as a degree to be granted to someone who had undertaken original research in the sciences or humanities. From there it spread to the United States, arriving at Yale University in 1861, and then to the United Kingdom in 1921. This displaced the existing Doctor of Philosophy degree in some Universities; for instance, the D.Phil. (higher doctorate in the faculty of philosophy) at the University of St Andrews was discontinued and replaced with the Ph.D. (research doctorate). However, some UK universities such as Oxford and Sussex (and, until recently, York) retain the D.Phil. appellation for their research degrees, as, until recently, did the University of Waikato in New Zealand.
In the US, the Doctor of Science, Sc.D., is an academic research degree that was first conferred in North America by Harvard University in 1872, and is relatively rarer than the Ph.D. However, the Sc.D. degree has long been awarded by leading institutions such as Harvard University, Johns Hopkins University, Massachusetts Institute of Technology, Boston University, Washington University in St. Louis, etc. At many of these universities, the academic requirements for the Ph.D. and Sc.D. are identical, and with identical doctoral academic regalia. In effort to standardize doctoral degree conferral at these large research institutions, the Ph.D. has replaced and grandfathered the Sc.D. in certain programs, while the Sc.D. is preserved in parallel to the Ph.D. as the highest conferred research doctorate.
Some ability to carry out original research must be documented by producing a dissertation or thesis, often of substantial length. The degree and title "doctor" is often a prerequisite for permanent (or nearly permanent) employment as a university lecturer or as a researcher in some sciences, though this varies on a regional basis. In others such as engineering or geology, a doctoral degree is considered desirable but not essential for employment.
While most US lawyers and physicians who pursue purely academic and research careers in law and medicine do so after having earned a J.D. or M.D., respectively, these degrees are regarded as professional doctorates because most who earn them pursue careers as working professionals. In more recent times other professional doctorates have emerged such as the EdD (usually held by school administrators), the DBA and the DPA (nearly always earned by prior recipients of the M.B.A. and the M.P.A., who continue to pursue ongoing professional careers in business and public administration) and the DPT (most often awarded to future physical therapy practitioners as an alternative to the usual M.P.T.).
In the United Kingdom and many Commonwealth countries like India, those training for the medical profession complete either a 5-6 year course or an accelerated 4-year graduate entry course that leads to the degrees of Bachelor of Medicine, Bachelor of Surgery (MBBS, MBChB, or other similar abbreviation); the higher postgraduate degree of Doctor of Medicine (MD) is reserved for those who can prove a particular distinction on the field, usually through a body of published work or the submission of a dissertation.
In India,MBBS/BHMS/BAMS /BNYS(garduate entry) medical degree is required to become a Doctor.The higher postgraduate Doctor of medicine(MD) is required to become a specialist in a particular field.
In the United States, those training for the medical profession complete a four-year undergraduate course of study and may continue on to earn either the doctoral level Doctor of Medicine (M.D.) degree or the doctoral level Doctor of Osteopathic Medicine (D.O.) degree. In other health-related disciplines such as physical therapy, pharmacy, podiatry, dentistry, chiropractic medicine, optometry, naturopathic medicine, Doctor of Nursing Practice, and veterinary medicine, where the professional doctorate is the degree which serves as the 'entry-level' degree for practitioners, a similar educational framework exists and leads to a doctoral degree. Such professionals typically use the title 'Dr' professionally and socially, although a podiatrist would often be referred to as a "podiatric surgeon" and a dentist a "dental surgeon".
Speaking in the House of Commons of the United Kingdom on January 19, 1996, health minister Gerald Malone noted that the title doctor had never been restricted to either medical practitioners or those with doctoral degrees in the UK, commenting that the word was defined by common usage but that the titles "physician, doctor of medicine, licentiate in medicine and surgery, bachelor of medicine, surgeon, general practitioner and apothecary" did have special protection in law.
For many years the UK's General Dental Council (GDC) regarded the use of the title doctor by dentists as a disciplinary offence, but on November 14, 1995 the GDC ruled that dentists could use the title doctor thenceforth provided that they did not do so to imply that they held qualifications that they did not possess.
In guidance issued by Who's Who published by A & C Black, it is noted that in the context of the UK, "not all qualified medical [practitioners] hold the [MD] degree" but that "those ... who have not taken [it] are addressed as if they had." A & C Black also note that British surgeons - a designation reserved for those who have obtained membership of the Royal College of Surgeons - are addressed as Mr, Mrs or Miss rather than Dr. This custom has been commented on in the British Medical Journal and may stem from the historical origins of the profession.
In German language-speaking countries, the word Doktor always refers to a research doctorate awardee, and is distinct from Arzt, a medical practitioner. An Arzt who holds the Dr. med. degree is addressed as Herr Doktor; an Arzt who does not would simply be Herr. This rule has been weakened recently, and people (e.g. in Austria) refer to medical practitioners as Doktor too.
In the Dutch language the word "dokter" refers to a physician, whereas "doctor" refers to a high academic rank.
Historically, lawyers in most European countries were addressed with the title of doctor, and countries outside of Europe have generally followed the practice of the European country which had policy influence through modernization or colonialization. The first university degrees, starting with the law school of the University of Bologna (or glossators) in the 11th century, were all law degrees and doctorates. Degrees in other fields were not granted until the 13th century, but the doctorate continued to be the only degree offered at many of the old universities up until the 20th century. As a result, in many of the southern European countries, including Portugal, Spain and Italy, lawyers have traditionally been addressed as “doctor,” a practice which was transferred to many countries in South America (as well as Macau in China).
The title of doctor has not customarily been used to address lawyers in England or other common law countries (with the exception of the United States) because until 1846 lawyers in England were not required to have a university degree and were trained by other attorneys by apprenticeship or in the Inns of Court. As such, lawyers in England were not doctoral candidates and had not earned the doctorate level degree. When university degrees became a prerequisite to become a lawyer in England, the degree awarded was the undergraduate LL.B.
Though lawyers in the United States do not customarily use such a title, the law degree in that country is the Juris Doctor, a professional doctorate degree, and some J.D. holders in the United States use the title of "Doctor" in professional and academic situations. In countries where holders of the first law degree traditionally use the title of doctor (e.g. Peru, Brazil, Macau, Portugal, Argentina, and Italy), J.D. holders who are attorneys will often use the title of doctor as well.
In many Asian countries, the proper title for a lawyer is simply, “lawyer,” but holders of the Juris Doctor degree are also called "博士" (doctor).
Customs for the use of the nouns "doctor," "a doctor," the stand alone form of address "Doctor," and the honorific "Dr. _____" vary throughout the world.
In Austria academic titles become part of the name and are therefore added to all personal ID documents. In certain legal transactions, such as land purchases, the person has to sign with the title, even if the person's usual signature does not include the title (has elected to omit it).
In Finland, the term tohtori is applied only to holders of the postgraduate research doctor's degree. The most common is filosofian tohtori (Doctor of Philosophy), but more specializations are used than in English (e.g. tekniikan tohtori "Doctor of Science in Technology"). The degree requisite for a physician's or dentist's license is called Licentiate of Medicine or Dentistry (lääketieteen/hammaslääketieteen lisensiaatti). The degree lääketieteen tohtori is the postgraduate "professor's degree". However, in rustic or old-fashioned unofficial usage, tohtori might refer to physicians also.
In France, the title of Docteur is only used by physicians, dentists, veterinarians and pharmacists. Confusingly, they do not hold a doctorate, which is in France only a research doctorate, but a "State Diploma of Doctor". The holders of a doctorate are never addressed as "Doctors", even in an academic environment.
In Germany, all holders of doctorate degrees are appropriately addressed as "Dr. _____" in all social situations. However, those granted PhDs from other countries may find themselves in legal difficulties if they use the term "Doktor" professionally in Germany.
Double doctorates are indicated in the title by "Dr. Dr." or "DDr." and triple doctorates as "Dr. Dr. Dr." or "DDDr.". More doctorates are indicated by the addition of "mult.", such as "Dr. mult.". Honorary titles are shown with the addition of "h.c.", which stands for "honoris causa". Example: "Dr. h.c. mult."
EU legislation recognises academic qualifications (including higher degrees and doctorates) of all member states. In Germany, a recent federal law (signed by all Cultural and Educational Ministers in accord with the EU law) confirmed the standardisation of qualifications. Until this Federal Law was introduced, there was no recognised mechanism to prevent administrators in private bodies and civil servants in public-funded bodies (such as universities) from automatically discriminating between the qualifications of people with German doctorates compared to holders of doctorates from an EU member state. The German university bureaucratic practice of using the post-nominal form, "Ph.D." (or equivalent), to distinguish non-German doctorates can be challenged legally as evidence of arbitrary discrimination and prejudice against non-German nationals (academics). All EU citizens are now "legally entitled" to use and be titled (addressed) as "Doctor" or "Dr." in all formal, legal and published communications. For academics with doctorates from non-EU member states, the qualification must be recognised formally ("validated") by the Federal Educational Ministry in Bonn. The recognition process can be done by the employer or employee and may be part of the official bureaucracy for confirming professional status and is dependent on individual bilateral agreements between Germany and other countries.
An example of mutual recognition of Doctor titles among EU countries is the "Bonn Agreement of November 14 1994", signed between Germany and Spain.
In Greece, the term "Doctor" (Δόκτωρ, Δρ.) is used to formally address both holders of a doctorate degree and physicians. The title "Διδάκτωρ" is used to reference holders of a doctorate degree, while the term "Ιατρός" is used for physicians of any specialty.
In Hungary the title of Doctor used to become a part of the name and is added as such to personal ID documents. The use of this practice has been significantly declined in the recent years, although legally it is still possible.
The first university of the western civilization, the University of Bologna, is located in Italy, where until modern times the only degree granted was that of the doctorate, and all other Italian universities followed that model. During the 20th century Italian universities introduced more advanced research degrees, such as the Ph.D., and now that it is part of the E.U. Bologna Process, a new 3-year first degree, or “laurea breve” (equivalent to a B.A. of other countries), has been introduced. The old-style "laurea" is now known as "laurea specialistica o magistrale" (master or specialistic degree, equivalent of a Master's degree). For historical reasons, even to this day, the title of "dottore/dottoressa" (abbrev. dott/dott.ssa) is awarded even to those who have attended a "laurea specialistica o magistrale". Upper levels of degree are anyway shown in the title, as those who obtain a master's degree can be referred as "dottore/dottoressa magistrale" (masterly doctor) while those who achieve the relatively new program of "dottorato di ricerca" (research doctorate, equivalent of a Ph.D.), carry the title of "dottore/dottoressa di ricerca" (researcher doctor)
In the Philippines, titles and names of occupations usually follow Spanish naming conventions which utilise gender-specific terms. "Doktór" is the masculine form, which retains the abbreviation Dr.; the feminine form is "Doktóra", and is abbreviated usually as "Dra."; others, however, some being Anglophones who wish to sound modern and Westernised, or some who advocate gender equality, would dispense with the distinction altogether. There does exist in Filipino an equivalent, gender-neutral term for the professional that carries the more general notion of "healer", traditional (e.g. an albuláryo) or otherwise: manggagámot.
In Portugal, up to recent times after the completion of an undergraduate degree - except in architecture and engineering - a person was referred to as doutor (Dr.) - male or doutora (Dra.) - female. The architects and engineers were referred by their profissional titles: arquitecto (Arq.) and engenheiro (Eng.).
Ph.D. Degrees are regulated by Royal Decree (R.D. 1393/2007), Real Decreto (in Spanish). They are granted by the University on behalf of the King, and its Diploma has the force of a public document. The Ministry of Science keeps a National Registry of Ph.D.s called TESEO . Any person who uses the Spanish title of "Doctor" (or "Dr.") without being included in this Government database can be prosecuted for fraud.
Unlike other countries, Spain registers a comparatively small number of Doctor degree holders. According to the National Institute of Statistics (INE), less than 5% of M.Sc. degree holders are admitted to Ph.D. programs, and less than 10% of 1st year Ph.D. students are finally granted a Doctor title. This reinforces the prestige that Doctors enjoy in Spain's society.
The usage of Doctor (ดอกเตอร์) or Dr (ดร.) has been borrowed from English. It can be seen as a title in academic circles and in the mass media. In contrast to other academic titles (Professor, Associate Professor and Assistance Professor), the use of Doctor as a title has not been recognized by the Royal Institute of Thailand. Therefore, this title, in theory, cannot be used officially. For example, in court of justice where strictly formal Thai language is used, Dr cannot be mentioned as a person's title.
In the United Kingdom, South Africa, Australia, New Zealand and other areas whose cultures were recently linked to the UK, the title Doctor generally applies in both the academic and clinical fields. "Registered medical practitioners" hold the degree of Bachelor of Medicine (usually also with surgery). Cultural conventions exist, clinicians who are Members or Fellows of the Royal College of Surgeons are an exception. As a homage to their predecessors, the barber surgeons, they prefer to be addressed as Mr, Mrs, Ms or Miss, even if they do hold a medical degree. When a medical doctor passes the examinations which enable them to become a member of one or more of the Royal Surgical Colleges and become "MRCS", it is customary for them to drop the "Doctor" prefix and take up "Miss", "Mister", or etc. This rule applies to any doctor of any grade who has passed the appropriate exams, and is not the exclusive province of consultant-level surgeons. In recent times, other surgically-orientated specialists, such as gynaecologists, have also adopted the these prefixes. A surgeon who is also a professor is usually known as "Professor" and, similarly, a surgeon who has been ennobled, knighted, created a baronet or appointed a dame uses the corresponding title (Lord, Sir, Dame). Physicians, on the other hand, when they pass their "MRCP" examinations, which enable them to become members of the Royal College of Physicians, do not drop the "Doctor" prefix and remain Doctor, even when they are consultants. In the United Kingdom the status and rank of consultant surgeons with the MRCS, titled "Mister", etc., and consultant physicians with the MRCP, titled "Doctor", is identical. Surgeons in the USA and elsewhere continue to use the title "Doctor", although New Zealand uses the titles of Mr and Doctor, in the same way as the United Kingdom.
In the state of Queensland, Australia, the use of the title "doctor" by health practitioners is restricted by legislation to medical practitioners, dentists or individuals holding a doctorate . Health practitioners who are not medical practitioners or dentists but hold a doctorate are prohibited from using the title doctor unless it is followed by the practitioner's name and letters or words indicating the doctorate held.
Queensland is the only state in Australia where the title doctor is legally restricted in this manner. This situation is likely to change with the introduction of a National Registration and Accreditation Scheme in Australia in the near future .
Canada lies somewhere between British and American usage of the degree and terminology of "doctor". Research doctorates - PhDs and ScDs - are entitled to use the title "doctor". In medicine, all medical practitioners trained in Canada receive the MD degree and are referred to as "Doctor". The British use of "Mr", "Mrs", and so on for surgeons is not followed in Canada. On the other hand, in the legal profession, graduates of almost all Canadian law schools receive the LLB degree and not referred to as "doctor" (in a growing number of Canadian law schools, including Osgoode Hall at York University, the degree of Juris Doctor is conferred, but the title is not used in practice). Medicine, Dentistry, and Law (as well as other first professional degree programs) are generally not considered to be graduate education in Canada, but rather a specialized professional undergraduate program. Practitioners in veterinary medicine, optometry and dentistry have doctorate degrees and are very commonly referred to with the title "Dr" preceding the specific name, but not referred to as "a doctor". Practitioners of podiatry and alternative medicine may not be referred to with the "Dr" honorific in relation to providing the public with health care services. In Ontario, only chiropractors, dentists, medical doctors, optometrists, psychologists, and registered Traditional Chinese Medicine practitioners and acupuncturists can use the title.  A registered naturopathic doctor may only use the title “doctor” in written format if he or she also uses the phrase, "naturopathic doctor" immediately following his or her name. Honorary degrees, usually LLD, are similar to those in the United States.
As one of the Commonwealth nations, Doctor title is commonly associated with medical doctor in first sense. Doctorate holders are entitled to be addressed "Dr." mostly in academic setting.
In the United States, the title "Dr." is commonly used professionally by those who have earned a doctorate-level degree, especially in academic settings. In addition, those who have been granted honorary doctorates are entitled to do so, especially in academic settings. The title is also commonly used socially by those holding a doctoral-level degree, although some would prefer to restrict usage of such a title to the professional setting, believing that its usage in a social setting unecessarily promotes social stratification.
The American College of Clinicians and at least one state recommends that health care professionals, including physicians, in the clinical setting use identification with an appropriate badge or name tag, as patients encounter a number of different practitioners. For example, all health care professionals should identify themselves and their profession when first meeting a patient.
Attorneys in the United States do not use any title, but instead use "Esquire" ("Esq."), "Attorney," or "attorney-at-law." This is despite the fact that the academic degree held by U.S. attorneys is called the Juris Doctor, a professional doctorate
In British English it is not necessary to indicate an abbreviation with a full stop (period) after the abbreviation, when the last letter of the abbreviation is the same as the unabbreviated word, while the opposite holds true in North American English. This means that while the abbreviation of Doctor is usually written as "Dr" in most of the Commonwealth, it is usually written as "Dr." in North America.
Similarly, conventions regarding the punctuation of degree abbreviations vary. In the United Kingdom, it is increasingly common to omit punctuations from abbreviations that are not truncations: while the usual abbreviation of "Esquire" is "Esq.", the usual abbreviation for "Doctor of Philosophy" is "PhD". It is not incorrect to use the fully-punctuated "Ph.D.", though if this pattern is used, it should be used consistently; practice in particular situations may vary, and it is always more elegant to be consistent with local patterns of usage than to deviate from them.
An honorary doctorate is a doctoral degree awarded for service to the institution or the wider community. This service does not need to be academic in nature. Often, the same set of degrees is used for higher doctorates, but they are distinguished as being honoris causa: in comprehensive lists, the lettering used to indicate the possession of a higher doctorate is often adjusted to indicate this, e.g. "Hon. Sc.D.", as opposed to the earned research doctorate "Sc.D.". The degrees of Doctor of the University (D.Univ.) and Doctor of Humane Letters (D.H.L.), however, are only awarded as an honorary degree.