Bending of light when it travels from one medium to another
The bending of light from one medium to another

When Ray of light enter from one medium to another it deviates from its path
When a light enters from one medium to another medium it will bend is known as refraction

Bending of light from orignal path is called refraction of light
The change of direction of light because of change of medium is known as Refraction or Refraction of Light. The ray of light changes its direction or phenomenon of refraction takes place because of difference in speed in different media.The light travels at faster speed in rare medium and at slower speed in denser medium. The nature of media is taken as relative. For example air is a rarer medium than water or glass.
When the direction of light is change when it passes ftom any medium is called refraction