What is the difference between yoga and stretching?

Many people perceive yoga as a great way to stretch out and become more flexible, and equally many people are put off because they feel they are not flexible enough (this is mentioned almost apologetically to me by some new students before they join my class). The goal of stretching is to become more limber, more flexible whereas the goal of yoga is to develop greater awareness - so it really doesn't matter that you are stiff to begin with. Awareness is an experience that can be measured by the ability to do different movements in different areas of the body at the same time. At first when we practice asanas (poses), we are captivated by the intensity of the stretch itself. But soon we become aware of more than just the stretch. We begin to sense subtle differences in the body. We see relationships in the body that have a large influence on our movement, physical ease, and even our mental state. This is the development of mindfulness that naturally comes from the physical practice of asanas and pranayama. Yoga is the development of awareness through physical practice - a meditation in action.