South Africa is a country of many languages and cultures. Education is mostly in English which implies that about 80% of all secondary school students are second language learners. Currently many mathematical problems are posed in real-life contexts. This not only introduces more language in mathematics texts, but also more issues related to culture. When considering the influence on readability, it is difficult to disentangle the role of linguistic and cultural factors and this in turn seems to be a manifestation of the Sapir-Whorf hypothesis. The study was therefore guided by research questions such as: what linguistic and cultural factors in the ordinary language of mathematics texts influence readability? Protocol analysis was used with students aged 17–18 years to establish readability problems. Linguistic as well as cultural factors were identified and the hypothesis that improved readability of mathematics assignments improves achievement was confirmed in a number of cases. Writers of mathematics texts should therefore consider linguistic as well as cultural factors when writing for different reading audiences. Other conclusions address teaching and examination practice.