Any specific interval of time in the archaeological record, such as the Upper Paleolithic period. This term is often confusingly used interchangeably with phase and stage. A period is a true time division of the history of a large region (such as the Valley of Mexico or southern China) and does not necessarily imply any developmental characteristics. In archaeological context, it is a major unit of prehistoric time, usually containing several phases and pertaining to a wide area. It is a convenient term used to discuss the history of a complex area.