-ist

(Greek > Latin: a suffix; one who believes in; one who is engaged in; someone who does something)

gastroenterologist
gastrologist
gastronomist
gelatologist
A misspelling of gelotologist.
gelotologist (s) (noun), gelotologists (pl) (gelatologist is incorrect)
1. A laughter researcher.
2. Someone who specializes in gelotology, the study of humor, laughter, and the exercising of the gelastic muscles, a deeply serious exploration of what happens to the physical systems; such as, respiration and circulation, when people are exposed to humor.

Gelotologists are serious people who study laughter, and they would be the first to tell you that the results of their research is very much a laughing matter.

genealogist
geobiologist
Someone who studies the biosphere or who specializes in the study of the interdisciplinary field of scientific research that explores interactions between the biosphere, the lithosphere, and the atmosphere.
geobotanist
Someone who studies the geographic distribution of plants.
geochemist
1. A science that deals with the chemical composition of and chemical changes in the solid matter of the earth or a celestial body (as the moon).
2. The related chemical and geological properties of a substance.
geochronologist
Someone who studies the chronology, or time periods, of the earth, as based on both absolute and relative methods of age determination.
geologist (singular), geologists (plural)
A scientist who specializes in the study of the origin, composition, history, structure, and processes of the earth.

One geologist claimed that geologists go to rock'n'roll concerts for entertainment and when they relax, they do it in a rocking chair; but their favorite kind of transportation is a rocket.

geomantist
Someone who foretells the future by using a system of divination by scattering pebbles, dust, sand grains, or seed on the ground and interpreting their shapes and positions.
geomorphologist
Someone who studies the surface configurations of the earth and the history of geologic activities as represented by such surface features.
geophagist
1. Someone who eats soil or earth; such as, clay.
2. Anyone who has a form of pica or the indiscriminate craving for and eating of substances; such as, paint chips, clay, plaster, or dirt.
geophysicist
A geologist who uses physical principles to study the properties of the earth.