Lexical cohesion in popular vs. theoretical scientific texts

Lexical cohesion, i.e. selection of lexical items which are in some way related to other lexical items in a text, contributes importantly to creating the texture, as defined by Halliday and Hasan (1976), and increases the overall coherence of the text. The article looks into different devices of lexical cohesion employed in scientific texts, namely reiterations (including exact repetitions and synonyms), use of superordinate expressions and general terms, and marginally also collocations. It is built upon an assumption that two basic types of scientific text, popular and theoretical ones, display some differences in the ratios between these lexical cohesive devices as well as in the frequency of their occurrence in each individual type. The analysis has been undertaken on two corpora of texts dealing with various topics in physics, comparing a text which is highly theoretical with one covering the same respective topic, adapted rather for didactic purposes or purposes of popular science. Lexical chains reveal the cohesive links between thematic elements of the texts and highlight the differences between individual texts matched in pairs. Particularly the use of general and superordinate lexemes in contrast to exact repetitions has proved to be the feature distinguishing between the two text varieties.