Black's Medical Dictionary first appeared in 1906. That new century was to see health care in the United Kingdom evolve from a largely personal, paternalistic consultation between doctor and patient, based more on medical tradition than medical science, to a complex, science-based, team-oriented and managed service. Even so, the core of medical practice has survived: the face-to-face consultation between doctor and patient. But the nature of this core activity has been irreversibly altered by a shift in the ‘balance of power’ between the participants as patients became better informed about their health, illnesses and possible treatments. A significant catalyst in the emergence of the informed patient has been the media, including publications like this dictionary. Societal changes have progressed, even since the 42nd edition, and the language now used attempts to reflect this. Treatment is no longer prescribed, nor instructions given but rather best evidence is recommended and advice offered.

One modest constant in this sea of change has been the objective of Black's Medical Dictionary. When launching the first edition, the editor, Edinburgh physician John D. Comrie, declared his aim as being to produce ‘a work which would occupy a position somewhere between that of a Technical Dictionary of Medicine and one intended merely for the domestic treatment of common ailments . . . [giving] information in simple language upon medical subjects of importance and general interest’. That initial mission-statement underpins this edition over 100 years later.

For the 43rd edition, every entry has been scrutinized and amended to ensure accuracy and precision; there are over 200 new entries, many of which reflect areas where medical practice is advancing most rapidly. Thus, immunogenetics and immunopharmacology are leading to new tests and new drugs aimed at an individual's genome rather than humankind in general. Hence, the dictionary includes entries for biologics, biosimilars, biomarkers and telomeres. Minimally invasive surgery and radiology have spawned a plethora of new procedures, many designated both by descriptive title and acronym. Old illnesses which were presumably too rare or abstruse for previous editions have exploded into public consciousness as international travel globalizes hitherto remotely confined diseases such as Zikavirus and MERS. Lifestyle changes mean that Bariatric Surgery and Maturity Onset Diabetes of the Young (MODY) appear for the first time.

Many of the statutory and most of the self-help organisations have changed their titles and their addresses. The NHS continues to reorganise unremittingly. The editor is aware of the anglocentric nature of the appendices dealing with these issues and hopes that readers in the other nations of the UK, Europe and elsewhere will exercise a degree of indulgence at the complexity of attempting to keep abreast of the ever-changing details of national institutions.

Recognising that readers will inevitably wish to seek medical information on-line and that dubious and misleading websites outnumber those that are well-informed and authoritative, a new appendix contains guidance to those sources which the editor considers most reliably evidence-based.