Second language learning is a field of research that focuses on understanding how individuals acquire proficiency in a second language after already mastering their native language. Researchers in this field study various factors that influence second language learning, such as age, motivation, cognitive abilities, cultural background, and teaching methods. They also investigate the cognitive processes involved in language acquisition, as well as how second language learners develop fluency, accuracy, and communicative competence. Overall, the goal of second language learning research is to improve instructional practices and facilitate more effective language learning experiences for individuals learning a new language.