-ist

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

essentialist
ethnobiologist
Someone who is a specialist in the study of ethnobiology or the study of ethnic groups as they are affected by the biological factors in their environment.
ethnobotanist
An ethnologist who studies relationships between people from various cultures and their plant life.
ethnogenist
A specialist in the study of the origins of human races.
ethnologist
An individual versed or skilled in ethnology.
ethnomusicologist
Someone who is a specialist in the study of traditional or folk music of a particular culture.
ethnoscientist (s) (noun), ethnoscientists (pl)
Someone who specializes in the study of the system of knowledge of nature and the physical world that has been produced by a other biologists or scientists.
ethnozoologist
A person who specializes in ethnozoology or the study of the complex relationships between people of various cultures and the animals in the same environments.
ethologist
ethonobotanist
etiologist
1. Anyone who studies etiology or the science of cause.
2. Someone who strives to find the causes of diseases via research and various forms of medical investigations.
etymologist (s), (noun), etymologists (pl)
A lexicographer who specializes in trying to reconstruct information about languages that are too old for any direct data can be known; since so many have no written records for examinations.

By comparing words in related languages, people may learn about their shared parent languages and in this way, some word roots have been found which can be traced all the way back to the origin of the Indo-European language family.

An etymologist is a scholar who knows the difference between an etymologist and an entomologist.

—Evan Esar, from Esar's Comic Dictionary;
Doubleday & Company, Inc.; Garden City, New York; 1983; page 206.
Eucharist (s) (noun), Eucharists (pl)
euphemist (s) (noun), euphemists (pl)
Someone who makes a substitution of an agreeable, an acceptable, or inoffensive expression for another one that may offend or suggest something unpleasant.
evangelist (s) (noun), evangelists (pl)
1. A religious person who travels from place to place to preach or a missionary; a revivalist or a promoter, organizer, or preacher at a religious revival meeting; especially, one for christians.
2. In the Mormon Church, a patriarch.
3. Etymology: the original sense of evangelist was "writer of a gospel"; from Greek euaggelion; and from Latin evangelium which in classical times meant "reward for bringing good news" based on the prefix eu-, "good, well" and aggelos "messenger" which is the source angel.