Verb form and rhetorical function in science writing: A study of MS theses in biology, chemistry, and physics

Variability in the grammatical profile of finite verbs, a feature which has been demonstrated across different genres of science writing, is here examined within one genre, reporting of research work in Master of Science theses. For this purpose, a sample of 20 theses in biology, chemistry, and physics was divided into five rhetorical sections (introduction, review, methods, results, discussion), and the use of finite verbs in each section, for each of three fields, was analyzed with respect to voice, tense, aspect, and modality. A number of significant differences emerged and were related to the changing content and communicative purpose of the discourse. The main findings include the following. Active verbs exceed passives in all rhetorical sections of the text except in methods, where passive verbs predominate. The present tense exceeds the past except in methods, and its frequency is very high in the introduction. There is uniformly little use of perfective and progressive aspects. The occurrence of modals is highest in the discussion and lowest in methods. Physics shows an interesting difference from biology and chemistry; there is no predominance of passive verbs in the methods section of physics theses, reflecting the more theoretical nature of research in that field.