Although a broad literature exists concerning the development of conceptual understanding of force and other topics within mechanics, little is known about the role and development of students' talk about the subject. The paper presents an in-depth investigation of students' talk whilst being introduced to the concept of force. The main research goal was to investigate and understand how students develop an understanding of the concept of force and how they use and understand the term "force". Therefore, we make relation to the research field of students' preconceptions and the field of second language learning. Two classes of students (N = 47) were videotaped during a time period of nine lessons, each transcribed and analysed using a category system. Additional data were obtained via written tasks, logs kept by the students, and tests. The detailed analysis of the talk and the results of the tests indicate that students face difficulties in using the term "force" scientifically similar to those in a foreign language instruction. Vygotsky already recognised a relationship between learning in science and learning a language. In this paper, important aspects of this relationship are discussed based upon empirical data. We conclude that in some respects it might be useful to make reference to the research related to language learning when thinking about improving science education. In particular, according to Selinker's concept of interlanguage describing language-learning processes within language instruction, the language used by the students during physics lessons can be viewed as a "scientific interlanguage". (Contains 6 tables, 4 figures, and 1 note.)