EN
Based on Polish and French vocabulary, this paper proposes criteria which shall make it possible to diHerentiate between prefixoids and prefixes. Uere are three such criteria: 1. prefixoids have the capacity to become autonomous (and even to become bases in word formation), and are impossible to substitute in their semantic representation by native prefixes, or to be expanded into full lexemes; 2. lexemes are created together with sufixoids, showing that neither of them are just afixes; 3. in some cases, the position of sufixoids can vary with regard to the lexical element which co-forms the compound lexeme. It is for these reasons that these elements deserve their own place in the morphological description of, at least, Polish and French.