 A common assessment of biodiversity-as-variety evaluates a set of protected areas and asks “how many different species are represented by that set of areas?” In the general framework, this converts to a more general biodiversity question: “how many different units are represented by that set of objects?” Thus, “species” corresponds to just one kind of “unit” of variation (with different species as different “units”), and areas are just one kind of “objects”. Biodiversity assessment considers a wide range of these possible objects for decision-making—not just areas, but also species, populations, and other entities. Biodiversity therefore can be quantified in general as a count of the number of different units represented by a given set of objects. Examples of other objects/units combinations include species/traits (or features) and species’ populations/genetic variants.