ok English is a free Android app designed to help users improve their English vocabulary. With over 7,000 words, it is a quick and efficient vocabulary builder, a reference dictionary, and a word-a-day app all rolled into one. The app provides access to a selected wordlist picked from the GRE, SAT, TOEFL, and IELTS official vocabulary master lists.

By default, the app introduces the user to a new word every day. To grow one's vocabulary, the app keeps track of the words the user has been exposed to (thereafter 'ok'ed) and tests them via quizzes using the spaced repetition system (SRS), which has been scientifically proven to optimize memorization and retention of learnt vocabulary. In addition, the app also functions as a simple and straightforward reference English dictionary with a default inbuilt search function.

Overall, ok English is a reliable resource for anyone looking to steadily increase and grow their English vocabulary on their own and at their own pace. With its user-friendly interface and effective learning techniques, it is an excellent app for students, professionals, and language enthusiasts alike.