Many students start upper secondary school with a lack of basic knowledge in mathematics from pri-mary school. The aim of this study is to investigate, analyse, illustrate and compare verbal language use in the introduction parts in two mathematics textbooks for upper secondary school to find out how comprehensible the texts are for readers with limited previous knowledge in mathematics. Previous research has shown that there is a connection between verbal language use in mathematical text prob-lems and students success in solving the problems (e.g. Bergvall, 2016). It has also been illustrated how revised versions of passages in textbooks with respect to the texts coherence highly increased readers possibility to acquire and recall the information (Beck et al., 1991). Based on theoretical per-spectives of learning, reading and comprehension of texts the analysis uses the concepts coherence, cohesion, main and subordinated speech-acts and macro-structures. What has been specifically ana-lysed is the theoretical explanations of fundamental concepts in arithmetic, algebra, percentages, ge-ometry and probability in the textbooks exponent and Matematik 5000. The results illustrate how many of the theoretical explanations in both textbooks lack in comprehensibility as a result of aspects such as massive density of mathematical terms, ambiguous or unclear links between the text units, lack of information about the content’s context and the inclusion of irrelevant facts. The results also show that the authors of the textbook Matematik 5000 seem to have been more engaged than the au-thors of the textbook exponent in the mission to connect new facts with the reader’s previous knowledge although exponent more than Matematik 5000 purports to be adapted for readers with a lack of secondary school knowledge of mathematics. The main conclusion of this study is that close inspection is needed of the learning potentials in textbooks intended for school education.