Vocab Assistant (http://www.vocabassistant.com/) is a conversational bot (yes, it talks to you via chat) which teaches you new English words based on your requirements and keeps track of your progress. It can teach new words (based on levels), help you revise old words that you have already learnt, show examples/synonyms/antonyms if you ask for, help you bookmark difficult words, etc. So, It is designed in such a way that people feel the comfort of learning from a real teacher.
