Question: I'm looking for a language learning tool that offers personalized vocabulary building and tracking progress.

Another good choice is Retention, geared for intermediate and advanced learners. It uses AI to generate exercises and to gather vocabulary, adapting to your level of proficiency and tracking your progress. With support for more than 20 languages, it's a relatively inexpensive subscription service good for keeping your language skills fresh over the long term.

If you prefer a more interactive approach, check out Talkio AI. The app offers simulated conversations with AI tutors, pronunciation practice in real time and an interactive wordbook to track your progress. It encourages you to communicate with native speakers and offers translations of what you're saying, so it can be a good way to get help with speaking.

Last is Praktika, which offers an AI-based 1-1 tutorship service for English language skills. It offers real-time conversations, immediate feedback and adaptive tracking of your progress in a human-like learning environment. It's a cheaper alternative to traditional tutoring, and it can be a good option if you want a more flexible, personalized experience.