Foremost, Yoga happens to be a discipline that originated from the Indian tradition, and it aids a person's well-being both physically and mentally. On the other hand, stretching is just a physical exercise that has to do with the stretching of your muscles to their highest extent in order to improve the tone and elasticity of the muscles.
This makes one's body to be very flexible and able to control your body motion to a particular extent. Yoga has to do with the principles of meditation in Buddhism, Jainism, and Hinduism. On the contrary, stretching is a concept that is brought about by the westerners.
Although yoga can be associated with some sorts of exercise in India, the true meaning is gotten from the root word "yuj", which means joining or union. Stretching is just simply an act of exercise that has to do with the skeletal muscles. Stretching is accepted worldwide, but yoga is not.