Gnomons are often described as the part of a sundial that casts a shadow, but there are many other synonyms for this word. Some of these include pointer, style, index, and indicator. These terms all refer to a device or tool that is used to measure time or track the position of the sun. Other synonyms for gnomons include obelisk, column, and monolith. These words typically refer to a tall, slender structure that is used as a marker or point of reference, and may have been used as a primitive form of timekeeping in ancient cultures. Whatever the specific term used, gnomons have played an important role in tracking time and measuring the movements of the sun for centuries.