Memrise is a free app for language learners (not just English) to enjoy learning vocabulary everyday. Being available for download on both App Store and Google Play, you can simply choose the language you want and start having fun with the words.
The app has a sophisticated system. To help you fully learn new words, the definitions are given with pictures and examples; at the same time, the word is pronounced so that you can get familiar with the native pronunciation. Later, there are different, tiny puzzles to help you interact with the new word; what's more, there are fun spelling and pronunciation quizzes too. All of these facilities are in an interesting package to show you when you need to study and what you have on the list.
There are many courses to choose from, so sign up and start expanding your vocabulary range.