According to Dictionary.com, a year is defined as the length of time it takes a planet to make a complete revolution around the sun. Since the sun does not revolve around itself, a year on the sun would have to be defined in different terms.
Scientists refer to the time it takes for the solar system to make a complete revolution around the center of the Milky Way galaxy as a galactic year. Estimates for the length of a galactic year range from 225 to 250 million terrestrial years. The sun also rotates. Based on the observation of sunspots, scientists have determined that the sun rotates once every 27 terrestrial days at its equator.