Anat.: The abbreviation for anatomy, the study of form. Gross anatomy involves structures that can be seen with the naked eye. It is as opposed to microscopic anatomy (or histology) which involves structures seen under the microscope. Traditionally, both gross and microscopic anatomy have been studied in the first year of medical school in the U.S. The most celebrated textbook of gross anatomy in the English-speaking world is Gray's Anatomy, still a useful reference book. The word "anatomy" comes from the Greek ana-meaning up or through + tome meaning a cutting. Anatomy was once a "cutting up" because the structure of the body was originally learned through dissecting it, cutting it up.