A diaphonemic inventory is a specific diasystem (a term popularized by Uriel Weinreich) that superimposes dialectal contrasts to access all contrasts in all dialects that are included. This consists of a shared core inventory and, when accounting for contrasts not made by all dialects (whether they are historical contrasts that have been lost or innovative ones not made in all varieties ), only as many contrasts as are needed. The diaphonemic approach gets away from the assumption that linguistic communities are homogeneous, allows multiple varieties to be described in the same terms (something important for situations where people have abilities in more than one variety), and helps in ascertaining where speakers make diaphonic identifications as a result of similarities and differences between the varieties involved.