-ist

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

pomologist
popularist
positivist (s) (noun), positivists (pl)
Anyone who emphasizes facts that can be proven scientifically rather than hypothetical origins of information: A positivist maintains that sense perceptions are the only legitimate admissible basis of human judgment and precise thoughts.

Some positivists say that valid insight depends on observable facts and the sciences, beginning with mathematics and concluding with the social behaviors of humans.

posologist
Someone who specializes in the creating of and mixing or combining of medical doses.
potamologist
A specialist in the study of rivers.
potruspytophilist
A collector of teapots or collections of teapots.
pragmatist
1. A person who takes a practical approach to problems and is concerned primarily with the success or failure of his or her actions.
2. A person who is oriented toward the success or failure of a particular line of action, thought, etc.; a practical person.
precisianist (s) (noun), precisianists (pl)
A person who attaches great or too great importance to being exact.
preexist (verb), preexists; preexisted; preexisting
To be present beforehand or to live prior to something else in a specific point of time: Dinosaurs inhabited the earth before mankind arrived, so they preexisted humans on earth.
primatologist (s) (noun), primatologists (pl)
A scientist who specializes in the branch of zoology that is concerned with the study of monkeys, the apes, and mankind, and their extinct predecessors: The famed primatologist, Dr. Travis, traveled extensively in the Americas, researching the common characteristics between Old World and New World monkeys.
proabortionist (s) (noun), proabortionists (pl)
A person who supports or is in favor of terminating pregnancies: Many proabortionists maintain that terminating a woman's pregnancy, although not a preferred family planning method, has always been used by women to gain control over their pre-birth conditions.

According to one view of proabortionists, women must have a safe and legal access to stopping their pregnancies because without this availability, women may use unsafe and illegal procedures that can result in serious injuries or death.

proctologist
projectionist
proliferophilist
A collector of miscellaneous items.
promorphologist
Someone who considers organisms and their parts geometrically.