-ist

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

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: A precisionist, or precisian, always holds fast to rules of conduct and doctrines, and without exception.
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, proliferophile (s) (noun); proliferophilists; proliferophiles (pl)
A collector of miscellaneous items: James, known to be a proliferophilist, had a lot of interests and loved to go to antique stores where he always found an unusual item or two, and therefore accumulated numerous objects over the years.
promorphologist
Someone who considers organisms and their parts geometrically.
proverbialist
Someone who originates, uses, or records proverbial sayings.
prudentialist
1. Someone who is governed by, or who acts from cautious motives when determining any action or line of conduct.
2. A reference to a person who is careful of the consequences of the actions that may result when he or she makes a decision to do something.
psammologist
psephologist
A political scientist who specializes in the study of elections; an electoral analyst or commentator.
psephomantist
Someone who uses stones or pebbles to divine or foretell the future.
pseudoantagonist (s) (noun), pseudoantagonists (pl)
A person who is not a real enemy or opponent: Jack was not really Sam's antagonist in the story, but the pseudoantagonist, Sam's friend and ally, and just played the part of Sam's rival.