Iconography is the description, classification, and interpretation of the subject matter of a work of art. Derived from the Greek words eikon, meaning image or icon, and graphia, meaning description, writing, or sketch, the word iconography is one of the least understood, most abused, and most flexible terms in the English language. Since iconography concerns itself with the subject matter and meaning of images in a very wide sense, it is nearly impossible to define its boundaries, and the term is now used to refer to areas outside of art history. This article deals exclusively with the Western world and does not refer to recent initiatives in the field in areas such as Asian, Buddhist, Chinese, or Native American iconography. Even though the term iconology was first referred to in the late medieval period and was brought into currency by scholars such as Aby Warburg and Erwin Panofsky at the start of the 20th century, it is usually seen as a separate area of research and will not be discussed here in detail. Recent work in the field of iconology has been significantly based on an anthropological approach to the work of art and has been spearheaded by such scholars as Hans Belting, Horst Bredekamp, Jean-Claude Schmitt, and others. The boundaries between iconography and iconology have become less clear over the centuries, and it is now frequently impossible to say where one begins and the other ends. In its truest meaning, iconology is the study of the work of art in its broadest context. Iconographical studies have now been applied to material that was previously considered outside of its remit. Instead of looking at traditional subjects such as animals or kingship it has now been applied to concepts such as light, sound, or narrative. This has been brought about because of the more holistic approach applied to studying works of art and our need to encompass elements outside of the work itself that also interact with it. As an intellectual activity, iconography starts with describing or reading an image, finding words that describe the content of that image, documenting what is seen, and trying to understand it. The verbal means we use to describe the visual range, from elaborate, evocative descriptions to short succinct words or codes; and many such standards exist. In the second half of the 19th century, photography began to reproduce works of art in quantity, and this impacted significantly on the development of art history and iconography as academic disciplines. The need to organize image collections into accessible and manageable subdivisions led to the creation of formalized and structured iconographic standards. One of the pioneering centers for the study of iconography is the Index of Medieval Art at Princeton University, which was founded in 1917 and still continues to support and direct research in the field as it has done for close to a century. From the 1940s onward, inspired by the Index and by library systems such as Dewey’s Decimal Classification, Henri van de Waal created the Iconclass system for the classification of iconographic subject matter, now a de facto standard used in many countries. Nowadays, the huge number of digital images has reinforced the need to use some form of subject access. Pattern recognition and automatic image annotation are only two of the directions in which researchers are working. The author would like to acknowledge Hans Brandhorst for his contribution to the article as well as colleagues in the Index of Medieval Art.