3. USING THE FIRST LANGUAGE IN TEACHING More than twenty years ago, a study carried out by Atkinson (1987) raised the debate on the role that the L1 plays in classrooms. In light of the preceding discussions, the education system has seen a growing effort to promote the use of L1 as a tool to support the learning and teaching of foreign languages. In order to achieve the greatest effectiveness, we need to understand how and when to integrate the L1 tool into the learning and teaching process.3.1 WHEN TO USE THE L1 IN THE CLASSROOM Before using the learner's L1 in the classroom , teachers need to know the criteria for deciding whether adopting L1 will be the best choice. Cook (2001) suggests considering four factors: effectiveness, learnability, naturalness and external relevance. Furthermore, he suggested that language teachers could decide when to use the student's L1 by asking four questions: Will the L1 used generate a more effective result? Can L1 really help with the acquisition of a second or foreign language? Does the learner feel more comfortable with the instructions given in L1? And will the use of two languages ​​create an authentic environment rather than a fake monolingual environment, and help students master the practical use of TL in real communication? Littlewood and Yu's (2011) study, which examined the focus of English teachers using L1 in classrooms in Hong Kong and mainland China, showed that teachers tend to use L1 in the following circumstances: to check the meaning and ensure understanding of the TL, to establish a friendly relationship in class and to manage behavior in class (ibid, 2011). . Teachers often practice using the L1 in many ways, but some similarities still exist from a framework of basic principles about...... middle of article ...... language use L1 and TL in class. Some will be willing to cooperate, others not. Teachers must therefore overcome difficulties to motivate students to use TL. This can be achieved by applying different teaching strategies such as diverse class organization, different teaching methods and policy implementation. With globalization and modernization, English as a global language is taught in many different contexts. Most English teachers are non-native speakers who teach English in their own country, where they share the same L1 with their students. By knowing the full advantages and disadvantages of using L1 in the classroom, as well as the techniques of using L1, it could be beneficial for teachers to master the positive use of students' native language and judicious use of L1. can even double the efficiency of the foreign language learning process.