Unimodality is a mathematical concept – there can be only one peak in a graph of a unimodal function. In archaeology the concept has been expressed in terms of "lenticularity" and "battleship shaped curves". For archaeologists, the concept expresses the idea that a style appears in the archaeological record, gains in popularity over time and then loses popularity until it vanishes from the record.
Unimodality has long been the basis for archaeological seriation, providing archaeologists a pattern to replicate in an attempt to order data chronologically. Mathematically, unimodality is all-or-nothing. The temporal distribution of artifacts or assemblages rarely exhibits strict unimodality and it is rarely possible to order artifacts to achieve perfect unimodality for multiple features. The lack of an objective measure of unimodality when perfect unimodality is not attainable has precluded consistently independently reproducible seriations.
OptiPath uses an objective, reproducible measure of unimodality (the Unimodal Index).