单语 is an educational and reference app developed by Kuixi Song. It is available for iPhone users and can be downloaded for free from the App Store. As a language learning tool, this app aims to help users build and expand their Japanese vocabulary.

The main features of 单语 include the ability to add new words manually or search for them online. The added words are accompanied by detailed information such as pronunciation, meaning, and part of speech. Users can also adjust the speed of the pronunciation and change the voice package. Additionally, the app allows users to create flashcards of the words for printing or offline review.

To reinforce learning, 单语 offers three different exercise options: recalling the meaning of a word from its Japanese reading, selecting the correct reading from a given meaning, or writing the Japanese equivalent of a given meaning. The app also provides the option to customize exercises based on specific word libraries, proficiency levels, accuracy rates, and parts of speech. Progress is tracked and displayed through practice records and a seven-day accuracy rate.

The app offers various personalization settings and the ability to share the app with friends. Users can also set reminders for daily word review. For added convenience, 单语 allows users to import vocabulary from popular Japanese textbooks and create custom word libraries. The app also supports Apple Watch, allowing users to browse all their words on the go.

For those who opt for the in-app purchase, 单语 offers online backup functionality, enabling users to upload their local word libraries to iCloud servers for easy access and retrieval.

Overall, 单语 is a comprehensive and user-friendly app that provides a convenient way to learn and expand one's Japanese vocabulary. Whether you are a beginner or an advanced learner, this app can be a valuable tool in your language learning journey.