-ist

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

educationalist
An expert in the theories or administration of education.
egoist (s) (noun), egoists (pl)
Someone who is devoted to his or her own interests and advancements: The egoist is someone who is motivated by self-interests.
One nice thing about egotists:
They don't talk about other people.
—Lucille S. Harper
electrologist
Someone who removes excess hair, moles, or other blemishes on the body by means of electrolysis.
electromagnetist
Someone who is a specialist or who is skilled in the field of electromagnetism.
electrometallurgist
Someone who studies or is a specialist in the field of electrometallurgy which is the branch of metallurgy that deals with the applications of electricity to metallurgical processes; such as, the use of electricity as a source of heat in refining metals.
electrorheologist
1. A specialist in the branch of physics concerned with the flow and change of shape of matter that is determined by electrical fields.
2. Someone who studies the flow of fluids under the influence of electric fields.
electrotherapeutist
1. A medical person who uses electricity in the treatment of disease.
2. A health-care provider who has specific training and experience in the therapeutic uses of electricity.
electrotherapist
1. A health care provider who has specific training and experience in the therapeutic uses or treatments with electricity.
2. Someone who specializes in the treatment of disease by electricity.
electrotypist
Someone who is skilled in electrotyping.
elocutionist
1. A public speaker trained in voice production, gesture, and delivery.
2. Someone who practices or teaches elocution.
emancipationist (s) (noun), emancipationists (pl)
Someone or those who advocate the freeing of human beings from slavery: The emancipationist, Harriet Elizabeth Beecher Stowe (1811-1896) wrote the novel Uncle Tom’s Cabin in 1852, which was focused on the abolition of slavery in the United States.
emotionalist
empathist
1. Anyone who uses intellectual identification with, or the vicarious experiencing of, the feelings, thoughts, or attitudes of another person.
2. Someone who has an imaginative response to an object; such as, a natural object or a work of art; or who shows feelings or attitudes which are present in oneself.
encyclopedist (s) (noun); encyclopedists (pl)
1. A compiler of or a writer for an encyclopedia.
2. Someone who attempts to deal with every branch of knowledge, or whose studies have a very extensive range.
endocrinologist
1. A physician who specializes in the diagnosis and treatment of conditions affecting the endocrine system.
2. A medically qualified specialist in internal medicine who has subspecialised in the diseases of glandular organs.