Aristotype

An arisotype in crystallography is a high-symmetry structure type that can be viewed as an idealized version of a lower symmetry structure. I believe Helen Megaw introduced the term in relation to perovskites which it is where it is still mostly used, the cubic perovskite structure (which is adopted at most half a dozen compounds) is regarded as the aristotype for the vast array of other lower-symmetry perovskites. Orig., a printing-out process using paper coated with silver chloride in gelatin; now, any such process using silver salts in either collodion or gelatin; also, a print so made.