-ist

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

saprobiologist
A biologist who studies saprobic environments or a reference to organisms that obtain their food directly from decaying organic material.
sarcologist
satirist (s) (noun), satirists (pl)
1. Someone who uses satire; especially, a writer of satirical works.
2. A person who writes or performs satires
scatologist
1. Someone who studies fecal excrement; as in medicine, paleontology, or biology.
2. Anyone who has an obsession with excrement or excretory functions.
3. A reference to a person who resorts to obscene language or literature; especially, that dealing pruriently or humorously with excrement and excretory functions.
secularist
1. An advocate of secularism; someone who believes that religion should be excluded from government and education.
2. Generally a reference to an ideology that promotes the secular; as opposed to the religious, particularly within the public sphere.
seditionist (s) (noun), seditionists (pl)
A person, or people, who strive to incite people to rebel against the authority of a state or monarch: "The man's speech to the group was enough to label him as a seditionist and it also resulted in his arrest by government agents."
seditionist (s) (noun), seditionists (pl)
A person who conducts or incites a rebellion against the authority of an established government.
segregationist (s) (noun), segregationists (pl)
Someone or those who separate or disconnect people or things from others: In the past, there were U.S. policies when government segregationists kept Indian nations isolated on their reservations.
seismologist
A specialist in the science of earthquakes and their effects.
selenographist
Someone who is skilled in selenography (descriptions of the physical features of the moon).
selenologist
Anyone who studies the nature and history of the moon.
semaphorist
Someone who manages or operates a semaphore.
semasiologist
Someone who studies the branch of linguistics that deals with the study of meaning, changes in meaning, and the principles that govern the relationship between sentences, images, or words and their meanings.
seminarist
seminist