The effect whereby the paths of rays of light (or other EM radiation from a distant source are bent by the gravitational effect of an intervening mass. With strong gravitational lensing, multiple images of the source are produced. The images are heavily distorted, and typically form arcs (or an Einstein ring) around the lensing mass. With weak gravitational lensing the resulting image is subject to a small distortion. [[../Chapters/Topic 3 Mapping the Universe]] [[Docent/S284 Astronomy]]