Vexillology is the scholarly study of flags. The term was coined in 1957 by the American scholar Whitney Smith, the author of many books and articles on the subject. It was originally considered a sub-discipline of heraldry, and is still occasionally seen as such. It is also sometimes considered a branch of semiotics. It is formally defined in the FIAV (Fédération internationale des associations vexillologiques) constitution as "the creation and development of a body of knowledge about flags of all types, their forms and functions, and of scientific theories and principles based on that knowledge." A person who studies flags is a vexillologist, and by extension, a person who designs flags is a vexillographer.
The word "vexillology" is a synthesis of the Latin word vexillum and the suffix –ology meaning "study of". The vexillum was a particular type of flag used by Roman legions during the classical era. Unlike most modern flags which are suspended from a pole or mast along a vertical side, the square vexillum was suspended from a horizontal crossbar along its top side, which was attached to a spear.
Vexillologists are active in dozens of national associations under the umbrella of FIAV (Fédération internationale des associations vexillologiques). Every second year, FIAV organizes the International Congress of Vexillology (ICV 2005 was in Buenos Aires, Argentina; ICV 2007 will be in Berlin, Germany. Internet activity of vexillologists is centered on the Flags of the World website and mailing list.