suppletive

... of optimus, meaning “best,” which in turn is the superlative suppletive form of bonus, “good.”

Article 11 of the Louisiana Civil Code provides the legal framework for the doctrinal distinction between imperative, or mandatory, and suppletive laws. Although neither term is included in the article, traditional civilian doctrine characterizes as imperative those legal precepts rooted in public policy which may not be set aside by private agreement. Suppletive laws, on the other hand, are those legal norms designed to supplement the parties' will in cases wherein its application is not excluded.