A language for special purposes (LSP) is used by specialists in a scientific or technical domain. It is characterised by its specialised lexica, syntax and semantics, which have often been the object of studies. Specialised discourse, much less well studied, also reveals specialised characteristics at the phrasal level. We examine the different levels of discourse specialisation that characterise both specialist and non-specialist LSP users, and how they are reflected in modality and use of terminological definitions. Specifically, we examine medical discourse in a comparable corpus of French and Japanese which includes two types of discourse, scientific and popular science. The modality analysis examines variations of the specialisation from the writer's point of view. We adapt an LSP model originally designed for general French, and apply it to Japanese. This required us to define a new typology composed of locutor groups that characterize the different modalities in the corpus. Terminological definition plays a central role when the LSP users do not share the same knowledge level; here, too, we determine a new typology elaborated from definitions for dictionaries and of phrasal constructions. For each category, we extract a list of markers that can be used for qualitative and quantitative analysis. In each of the two languages, we show that the two types of discourse can be distinguished either by the frequency and content of modality markers, or by the distribution of definition categories. This typology can potentially be used to create terminological resources, or to update existing resources in the context of scientific abstracting and gisting.
