Lexical morphology is barely attended to in the teaching of vocabulary in primary schools. If and when it is addressed, it is generally via derivation and composition and, unfortunately, looking to exploit pupils’ etymological knowledge which is inexistent. This article proposes to present to Robert Brio dictionary (2004). This dictionary, which is relatively unknown, allows an alternative means of studying morphology: without recourse to classical languages and using a comparative approach to analyzing words. This article is divided into three sections: theoretical (presentation of the theoretical and methodological options of the Robert Brio), lexicographical, pedagogical (discovery of patterns favouring in particular the acquisition of lexical spelling).