Many species have synonymy with genus "Psoralea". These three genera were duly sunk into synonymy with "Vitex". The recognised synonymy of the genus was published by Theodore S. Palmer in 1904. Recently, the synonymy of the two genera is generally accepted. Some species have been transferred to other genera, with others reduced to synonymy. Many genera, such as "Lomatophyllum", have been brought into synonymy. Some relations between lexical items include hyponymy, hypernymy, synonymy, and antonymy, as well as homonymy. A second suggestion Quine considers is an explanation of synonymy in terms of interchangeability. Some semantic relations between these synsets are meronymy, hyponymy, synonymy, and antonymy. Johnson gave evidence of the synonymy of the two species. The species' wide distribution and consequent genetic drift has led to an extensive synonymy. But does interchangeability hold as an explanation of cognitive synonymy? The operational definition of synonymy depends on the distinctions between these classes of sememes. The objection to synonymy hinges upon the problem of collateral information. This plant has a convoluted history of synonymy with "Inga vera".