“…Hence, L1 has already been used in English language classes, and ESP classroom is not an exception, as it facilitates learners" understanding and provides sense of security, better comprehension and progress, higher achievement, and a positive learning atmosphere (Auerbach, 1993;Bruen & Kelly, 2017;Butzkamm, 2003;Usadiati, 2009). L1 also contributes to language skills development, metalinguistic awareness, negotiation of meaning, reduced cognitive overload, lower affective barriers such as anxiety, and higher self-confidence and self-motivation (Berning, 2016;Boustani, 2019;Bruen & Kelly, 2017;Cheng, 2015;Cuartas Alvarez, 2014;Luchini & Rosello, 2007;Usadiati, 2009). Therefore, although "the use of L1 has been gradually viewed less favorably by second language (L2) teaching theorists after the Grammar-Translation Method lost its prominent role" (Du, 2016, p.359), the interest regarding whether to include learners" L1 in teaching has gained recognition and become a persistent research topic particularly after being neglected for many years within the communicative approach beginning in 1970s.…”