threshold function: a function that takes the value 1 if a specified function of the arguments exceeds a given threshold and 0 otherwise
function: (mathematics) a mathematical relation such that each element of a given set (the domain of the function) is associated with an element of another set (the range of the function)
sophora: cosmopolitan genus of trees and shrubs having odd-pinnate leaves and showy flowers; some species placed in genus Podalyria