Abstract
The acquisition of discourse markers (DMs) by undergraduate students of English for Specific Purposes (ESP) constitutes a research problem that has not been thoroughly investigated from the vantage point of sustainable practices associated with the explicit and implicit modes of instruction. In the article, we present a quantitative study aimed at uncovering whether the acquisition of DMs would be sustainable within the period of one semester. To this end, the material of the study involves a corpus of descriptive essays written by a group of ESP undergraduates whose first language (L1) is Ukrainian and another foreign language is Russian (hereafter referred to as participants). One part of the corpus was written by the participants during the explicit mode of instruction, whereas another part was written during the implicit mode. The corpus was analysed using the software program AntConc (Anthony, 2022) to examine possible changes in the frequency of DMs over time. The quantitative investigation of the participants’ essays revealed the following key findings: while the explicit mode of instruction was associated with a substantial increase in the frequency of the occurrence of DMs in the participants’ descriptive essays, the implicit mode of instruction led to an abrupt decrease in the frequency of DMs as well as the narrowing of their repertoire. The findings, the novelty of the study and the pedagogical implications that arise from the findings are further discussed in the article.