The grammar sharpener (https : / / thegrammarsharpener . com) is an interactive grammar website that helps you avoid common errors in English. We have compiled a list of over common errors made by English language learners and used these to create tests each with items. These tests will give you , learning opportunities to activate and expand your knowledge of English grammar. To make your learning interesting, we have used a variety of different test types, each designed to help you learn. Each question provides grammar notes and feedback on your answers.