Violet shift is a term used in astronomy to describe the change in color of astronomical objects that occurs due to their relative motion. Some synonyms to describe the same concept include blueshift, redshift, and Doppler shift. Blueshift is used when the object is moving towards the observer, causing its light to shift towards the blue end of the spectrum. Redshift, on the other hand, is used when the object is moving away from the observer, causing its light to shift to the red end of the spectrum. Doppler shift is a more general term that encompasses both blueshift and redshift, and refers to the change in frequency of any type of wave as a result of relative motion.