Traits-based community analyses are receiving increasing attention. However, consistent interpretation of empirical results and ecological understanding in stream ecology are limited by ambiguous terminology. Furthermore, the measurement scales used to analyze trait data, especially ordinal-scale data, are often inappropriately applied. We identify and discuss these shortcomings and offer a solution for an operative and algebraically correct treatment of traits and a unified nomenclature that facilitates direct comparison among traits-based studies. A unified terminology allows for logical translation among existing, alternative trait nomenclatures and should facilitate communication of research findings among stream ecologists and more directly connect stream traits-based research with general ecology.