Reverse Dictionary - Describe a concept and get back a list of words

Duolingo - Duolingo is a free language learning app for iOS, Windows and Android devices. The app makes learning a new language fun by breaking learning into small lessons where you can earn points and move up through the levels. Read more about Duolingo.

Writefull Thesaurus - A Google Docs add-on that uses AI to give you synonyms

Lingvist - Lingvist helps you take your foreign language skills to the next level with a broad selection of exercises and lessons.

Dictionary Anywhere - Dictionary Anywhere is an open-source and easy-to-use browser extension for Mozilla Firefox and Google Chrome that allows you to check definitions easily while browsing the web.

Drops - Visual language learning.