-ist

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

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 (s) (noun), ecoactivists (pl)
One who actively opposes the pollution of, or tries to prevent damage to the living world: An ecoactivist can also be described as an environmental activist or an environmental campaigner.
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
educationalist
An expert in the theories or administration of education.