Abstract : This thesis attempts to explore the relationship between language disorders and the way they are named by speech and language therapists. The French labels dysphasie, troubles spécifiques du langage écrit, aphasie, difficultés à l'apprentissage du langage écrit, dyslexie, retard de langage, relating to Specific Language Impairment, disorders of the written language, aphasia, dyslexia... belong to speech and language therapy (SLT) terminology and have always evolved following theoretical movements. In order to describe the inconsistency of the link between diagnostic labels and the reality of the labelled pathology, some epistemological, lexicological and terminological issues have been explored. Assessments enable SLT practitioners to make a diagnosis, following which they write a report (CRBO). These reports can be considered as the reflection of the representations speech and language therapists (SLTs) have of the disorders, and show how they use their own terminology. 435 authentic reports have been semi-automatically analysed descriptively using lexicological and terminological tools. The XML encoding captured the current use of the terms describing any pathology encountered by SLTs. The results show two terminological groups (one relating to the nature of the disorder, the other relating to its form), which illustrate the necessary nuances the SLT uses with these collocational phrases. The final phase of the analyses helped to produce a framework for a new speech and language therapy classification based on clinical practice (COFOP).