What is the best language learning app?

As an AI language model, I don't have personal preferences. However, based on the most popular applications, here are some information about the best language learning apps:

1. Duolingo - offers a gamified experience that encourages learners to complete daily lessons and earn points. It's free to use and offers a variety of languages.

2. Babbel - sets itself apart from others by focusing on conversational skills. It's subscription-based and offers a range of languages.

3. Rosetta Stone - uses an immersive approach to language learning that mimics how people learn their first language. It's also subscription-based and offers a variety of languages.

4. Memrise - uses memory techniques such as flashcards and spaced repetition to help learners retain new vocabulary. It's also free to use and offers a range of languages.

5. Lingodeer - offers courses in Asian languages such as Japanese and Korean. It's a subscription-based app that aims to make learning a new language fun and easy.

Overall, the best language learning app for each learner may vary depending on their goals, budget, and language proficiency level. The key is to find an app that offers an engaging and effective learning experience that fits your needs.