Adjective
English Wikipedia has an article on:biorthogonal systemWikipedia
biorthogonal (not comparable)
(mathematics) Describing a pair of topological vector spaces that are in duality with a pair of indexed subsets in a specific manner
For example, JPEG 2000 is an image compression standard that uses biorthogonal wavelets. Source: Internet
They are called biorthogonal functionals. Source: Internet