Literature review

2.1.4 Challenges in learning English vocabulary
Sesame words can be challenging to learn because they are hard to recall, easily forgotten, difficult to apply in various situations, and have numerous definitions. This makes students confused when they look up the definitions in the dictionary. The cause is that students forget how many words they have acquired because they learn by topics rather than going back and reviewing earlier topics. The process of learning vocabulary through stories and novels aids in word retention based on context and increases interest in reading and learning English. According to each student's reading ability, the Bookworms and Xreading series are reputable and authoritative reading resources.
2.2.1 The scope of Duolingo, wordup
2.2.1.1 The scope of Duolingo
a. Definition of Duolingo
The most well-liked method of learning languages worldwide is through the Duolingo language learning program. The goal of the business is to create the finest education possible and make it accessible to everyone. Duolingo makes learning enjoyable and is effective, according to study. You will acquire practical communication skills while earning points and progressing to new stages with the help of brief, bite-sized lessons. The business also developed the Duolingo English Test, an accessible and cost-effective language certification option that is recognized by thousands of institutions around the globe, in addition to its language learning appcore platform.
b. Advantages and disadvantages of Duolingo
* Advantages

• 
  Suitable for everyone learning English
  

Duolingo is an English learning platform that is perfect for everyone because its lessons are personalized. Duolingo continuously asks learners if the pace and level of the lesson is appropriate to personalize learning based on the learner's pace. And with Duolingo, learners on the platform, even those who are just starting to learn English, don't need to worry about the speed and level of the lesson.

• 
  Help learners memorize vocabulary
  

In addition, Duolingo lessons use the Spaced Repetition technique. This is a technique that uses the repetition of knowledge to be learned over long periods of time and this technique is intended to take advantage of the characteristics of human psychology and memory. Duolingo lessons are always aimed at memorizing learners' vocabulary, so Duolingo always repeats that vocabulary. With the application of this technique, learning English, especially in learning and memorizing vocabulary, will be extremely effective.

• 
  Reduce stress in the process of learning English
  

Because Duolingo is designed as a game, the learning process of learners will be extremely relaxing. Duolingo also makes learning experiences fun and motivating by offering extra features like podcasts, stories, or leaderboards to compete with other learners.

• 
  Convenience in learning English
  

Duolingo is an extremely convenient English learning application because learners can learn on computers or even on their phones. Learners can take the time to learn anytime and anywhere.