In Adioukrou complex constructions, èké as a lexical item plays an important role. Previous works identified èké as a relativizer and a complementizer. Quite recentely, by concentration on data from Adioukou language and cross-linguistic comparison of subordination, I discovered the fundamental characteristic of èké: its polyfunctionality. The descriptive perspective and the process of grammaticalization explain and reinforce this new finding. In Adioukou, syntactically, there is no clear-cut distinction between finite and non-finite complement clauses. While English has a complex system of finite and non-finite complement clauses such as that-clause, wh-clause, to infinitive, bare infinitive, and participle, Adioukrou prefers using èké in those syntactic constructions as well as in subordinate clauses. èkéencodes also both concrete object and abstract matter, whereas Japanese no and koto encode respectively an event and a proposition.