Introduction Duolingo Duolingo is a free language-learning platform, which provides languages from different countries for learners to learn in multiple countries. In addition to providing learners with language practice, Duolingo also provides a service for after-class practice to assess the proficiency of users in language learning. The reason why I use "Duolingo" in teaching There is a great design for this language learning platform, that this has a vocabulary module to let users review vocabulary which has learned. Learners earn "points" when they learn a language, such as when they complete a course when the learner completes all relevant courses that the learner will be identified as "achievement achievement".Each course has a mechanism for setting rewards, and 3 points will be deducted if you make a mistake. In the early course, the learner will have 4 "lives" at the beginning, and the later course will be reduced to 3, and every...