-ist

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

dramatist
A writer of plays; a playwright.
dramaturgist
A composer of a drama; a playwright.
dualist
duelist
duopolist
A member of a duopoly.
dynamist
ecclesiologist (s) (noun), ecclesiologists (pl)
Someone who specializes in theological doctrines relating to churches: "Abraham was an ecclesiologist who studied theology as it was applied to the nature and structure of Christian Churches."
eclecticist
Someone who selects according to the eclectic method; such as, in philosophy or architecture.
ecoactivist
One who actively opposes the pollution, or destruction by other means, of the environment.
ecofeminist
Of, relating to, or characteristic of ecofeminism; advocating or adhering to ecofeminism.
ecologist
One who specializes in biological sciences that deal with the relationship between organisms and their environment.
economist
1. One who manages a household; a housekeeper.
2. Someone who studies, works, or is an expert in the field of economics.
ecotoxicologist
A specialist in the harmful effects of chemicals to the natural environment.
ecozoiatrist
A veterinarian dealing with wild animals.
ecumenist