The number of species present at a particular place and time. No assumptions are made about the relative abundance of these species. It is not possible to enumerate all species in a community then it become necessary to distinguish between numerical species richness, which is defined as the number of species per specified number of individuals or biomass, and species density, which is the number of species per specified collection area.

A game in which players assume the roles of characters in a fictional setting. Players take responsibility for acting out these roles within a narrative, either through literal acting or through a process of structured decision-making or character development.