The study of the shape of artefacts. It has two main purposes: firstly, classification. All examples of a given class of object, for instance flint knives, axes, pottery jars or anything else, can be grouped according to their shape. Such a grouping is called a type series and, once this is prepared, further examples can be described simply by references to types already recognised. The distributions of the types in space and time can often be studied with greater advantage than that of the whole class. The technique is necessarily subjective. Attempts to produce purely objective classifications have so far met with little success.
Seconldy, comparisons of different types will often show which are more closely, which more distantly, related, in exactly the same way that taxonomy classifies and relates the species of the animal and vegetable kingdoms. Taking this further, the relationships between similar types can sometimes be shown not merely to classify, but also to explain, their development. This process is known as seriation. It may show increasing complexity or functional improvement, simplification and functional or artistic decline, or change for neither better nor worse subject solely to fashion. The direction of change may be shown by the loss of function or the different technique of manufacture but will usually need to be determined by other evidence: stratigraphy or independent dating of two or more members from the series. This would be essential for fixing the rate of change.