In order to have a clearer understanding of the range of speech variations in both healthy and disordered speech populations, and in different speech conditions, the objective of this project is three-fold. It aims to draw a typological inventory of normal and abnormal speech variations, to test the adaptability of healthy and pathological speakers to different performance conditions (controlled to less controlled situations), and to test the conditioning effect of various linguistic-communicative constraints on these variations across populations. In parallel, our project aims to improve automatic speech processing systems confronting them to non prototypical speech (spontaneous or disordered speech). The examination of speech production in natural conditions has led to the observation of a large variety of non-prototypical pronunciations and has shown that these speech variations are not only the results of physiological or phonological factors but also of higher-level linguistic-constraints. Understanding the role of these constraints and the way they interact is challenging. Basic tenet of this proposal is that observation of disordered speech can inform the way normal speech is produced and vice-versa. Hence, one of the hypotheses raised in this project is that the forms of variation in disordered speech and their localization in the speech chain can inform the range and sites of possible normal variation. A comparison of how healthy and pathological speakers adapt their production to different speech conditions (here read vs. spontaneous speech) is also a way to better understand the processes and constraints at play during speech production. Two groups of patients suffering from motor speech disorders affecting different levels of production (planning in apraxia of speech and execution in dysarthia) are compared to healthy speakers. Read and spontaneous corpora will be designed and enriched at various levels ranging from phonetic alignment to discourse marker annotations. A combination of manual and automatic methods will be used to analyze the data. Outcomes of this research proposal will contribute to a better description of the form of variation occurring in the French language and to further explore the blurred boundary between normal and abnormal speech variations. It will improve our knowledge on both healthy and disordered speech variants, and on the speakers' ability to modulate their production to speech situations. This project is original in the way it proposes a new approach path to the question of the variability in the output of a healthy speech production system through a confrontation with the variability imposed/entailed by a disordered system. The two populations are not only considered as control conditions of each other but are studied in parallel. New contributions to the understanding of pathological signs in speech motor disorders and the definition of normal and abnormal speech patterns will be also achieved from the consideration of different speech styles, of the adaptability of speech performance, and on the role of the different constraints imposed to the production system in natural communication situations. Moreover, the proposed adaptation of approaches and methods developed for the study of healthy speech (elicitation and large corpora analysis techniques, multi-level annotations, automatic processing tools, etc.) to disordered speech constitutes a novel and stimulating methodological challenge. Finally, another interest of this project is its pluri-disciplinarity. The outstanding blend of competences in phonetics, phonology, prosody, clinical phonetics, clinical practice, speech engineering which are united in the proposed consortium are an essential part for the good progress of the project.