Research has shown that science education is highly dependent on the quality of teaching materials. Here science textbooks have a dominant role in Swedish schools. When curriculum determines the content of textbooks, it promotes confidence in both schools and teachers. The purpose of this study is to analyze physics textbooks by using Järnborg’s (2007) theoretical concepts of categorization of the subject-specific words. The following questions are posed: * Which subject-specific concepts are presented in three selected physics textbooks for grade 4-6 in Swedish public schools? * How are these subject-specific concepts presented? The study finds a variety and selection of material presented in the selected textbooks. The results show that physics concepts are introduced through describing the concept by example and through the relation between the new and earlier introduced concepts. Consequently, it is important for teachers to take into consideration the content and structure of a textbook in science in order to realize its potential in the classroom