rationel

Rationel is a term that can refer to more than one concept depending on language and context. In French, the standard adjective is rationnel, meaning rational or reasonable, and derived from Latin rationalis. The form rationel can appear in older texts or as a brand name, but it is not the conventional spelling for the French word.

Rationel is also the name of a Danish manufacturer in the building products sector. The brand markets windows and doors designed for energy efficiency and contemporary design, often featuring timber or mixed-frame constructions with modern glazing. As a brand, Rationel is associated with functional performance, durability, and aesthetic compatibility with Northern European architectural styles. Products bearing the Rationel name are distributed in several European markets and are positioned within residential and light commercial applications.

Because of the different uses, the term may appear in contexts ranging from linguistic discussion to branding. When referring to language, the French concept is usually spelled rationnel; when referring to the Danish company, the brand uses the capitalized form Rationel. Outside of these specific senses, the lowercase form rationel may be encountered as a typographical variant or branding choice, but it is not established as a standard term in either language.