This study investigated the use of lexical bundles in research articles written in English by Turkish scholars. For the purpose of the study, a corpus of published research articles produced by Turkish scholars in six different academic disciplines was collected. The four-word lexical bundles that appeared at least twenty times in this one million word corpus were identified and further analyzed both structurally and functionally based on the previous taxonomies developed by Biber, Johansson, Leech, Conrad and Finegan (1999) and Biber, Conrad and Cortes (2004). The results of this study revealed that the lexical bundles found have structural correlates as well as strong functional features that help to construct discourse in academic writing. The conclusions drawn from this study could be applied to the teaching of academic genres to researchers in English as a Foreign Language context and are expected to provide insights for further corpus-based studies in academic writing.

Cette thèse se propose d’étudier la grammaticalisation, processus d’évolution linguistique par lequel les éléments fonctionnels de la langue se trouvent remplacés au cours du temps par des mots ou des constructions de contenu, c’est-à-dire servant à désigner des entités plus concrètes. La grammaticalisation est donc un cas particulier de remplacement sémantique. Or, la langue faisant l’objet d’un consensus social bien établi, il semble que le changement sémantique s’effectue à contre-courant de la bonne efficacité de la communication ; pourtant, il est attesté dans toutes les langues, toutes les époques et, comme le montre la grammaticalisation, toutes les catégories linguistiques. Dans cette thèse, nous étudions d’abord le phénomène de grammaticalisation d’un point de vue empirique, en analysant les fréquences d’usage de plusieurs centaines de constructions du langage connaissant une ou plusieurs grammaticalisations au cours de l’histoire de la langue française. Ces profils de fréquence sont extraits de la base de données de Frantext, qui permet de couvrir une période de sept siècles. L’augmentation de fréquence en courbe en S concomitante du remplacement sémantique, attestée dans la littérature, est confirmée, mais aussi complétée par l’observation d’une période de latence, une stagnation de la fréquence d’usage de la construction alors même que celle-ci manifeste déjà son nouveau sens. Les distributions statistiques des observables décrivant ces deux phénomènes sont obtenues et quantifiées. Un modèle de marche aléatoire est ensuite proposé reproduisant ces deux phénomènes. La latence s'y trouve expliquée comme un phénomène critique, au voisinage d’une bifurcation point-col. Une extension de ce modèle articulant l’organisation du réseau sémantique et les formes possibles de l’évolution est ensuite discutée. / This work aims to study grammaticalization, the process by which the functional items of a language come to be replaced with time by content words or constructions, usually providing a more substantial meaning. Grammaticalization is therefore a particular type of semantic replacement. However, language emerges as a social consensus, so that it would seem that semantic change is at odds with the proper working of communication. Despite of this, the phenomenon is attested in all languages, at all times, and pervades all linguistic categories, as the very existence of grammaticalization shows. Why it would be so is somehow puzzling. In this thesis, we shall argue that the components on which lies the efficiency of linguistic communication are precisely those responsible for these semantic changes. To investigate this matter, we provide an empirical study of frequency profiles of a few hundreds of linguistic constructions undergoing one or several grammaticalizations throughout the French language history. These frequencies of use are extracted from the textual database Frantext, which covers a period of seven centuries. The S-shaped frequency rise co-occurring with semantic change, well attested in the existing literature, is confirmed. We moreover complement it by a latency part during which the frequency does not rise yet, though the construction is already used with its new meaning. The statistical distribution of the different observables related to these two phenomenal features are extracted. A random walk model is then proposed to account for this two-sided frequency pattern. The latency period appears as a critical phenomenon in the vicinity of a saddle-node bifurcation, and quantitatively matches its empirical counter-part. Finally, an extension of the model is sketched, in which the relationship between the structure of the semantic network and the outcome of the evolution could be discussed.