A term used to describe a number of cultures or industries broadly related in time and space and yet which are discrete entities. Some type of intergroup relationship, common ancestry, or similarity of interaction with the environment is implied. In American terminology, series is a broad unit of classification embracing a number of related cultures or pottery styles. A series has both duration in time, when one culture or style develops into another, and extent in the space (the area occupied by the various cultures or styles making up the series).