Achondrites are a type of stony meteorite that do not have chondrules - small, spherical grains that are found in many other meteorites. There are several synonyms for achondrites, including non-chondritic meteorites, as well as differentiated meteorites and igneous meteorites. This is because achondrites are believed to have originated from the larger bodies in the asteroid belt, where processes such as differentiation - the separation of materials based on their density - and melting occurred. These processes resulted in the distinct properties of achondrites, making them a valuable source of information about the formation and evolution of the early Solar System.