If users can’t figure out how to use your mobile applications and what’s in it for them, they’re gone. Usability and UX are key factors in keeping users satisfied so understanding, measuring, testing and improving these factors are critical to the success of today’s mobile applications. However, sometimes these concepts can be confusing—not only differentiating them but also defining and understanding them. Philip Lew explores the meanings of usability and UX, discusses how they are related, and then examines their importance for today’s mobile applications. After a brief discussion of how the meanings of usability and user experience depend on the context of your product, Phil defines measurements of usability and user experience that you can use right away to quantify these subjective attributes. He crystallizes abstract definitions into concepts that can be measured, with metrics to evaluate and improve your product, and provide numerous examples to demonstrate the concepts on how to improve your mobile app.