-ist

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

tonometrist
Someone who uses an instrument, such as a graduated set of tuning forks, to determine the pitch or vibration rate of tones.
toponymist
A person who utilizes a place-name, or a name given to a person or thing, marking its place of origin.
toxicologist
toxophilist
A collector of bows and arrows.
trachelologist
A specialist in the study of the neck and its injuries and diseases.
tractenjophilist
A collector of steam rollers.
tragematopolist
1. A seller of sweets; such as, candy or dried fruit.
2. Confectioner, someone who makes confections (sweet preparation of fruit, candy, cakes, cookies, etc.) to sell.
transcendentalist (s) (noun), transcendentalists (pl)
1. Someone who believes that reasoning is the key to understanding reality: One of the most famous transcendentalists was Ralph Waldo Emerson who believed and wrote about the importance that everyone should be self-reliant or self-sustaining.
2. Anyone who asserts that true knowledge is obtained by faculties of the mind that go beyond sensory experiences: Margaret Fuller, a transcendentalist of the 19th-century, was one of the philosophers who advocated that the spiritual reality rises above the scientific and empirical facts and entities of this world.
traumatologist (s), traumatologists (pl) (nouns)
A surgeon who practices traumatology, or a medic who is on duty at a trauma center.
tribologist (s) (noun), tribologists (pl)
A specialist in the science of the mechanical functions of friction on reacting surfaces.
trichologist
1. A specialist in the study of hair structure and diseases.
2. By extension, a hairdresser or hair stylist.
tricologist
1. Someone who specializes in the study and treatment of hair and related problems.
2. A hairstylist who is trained specifically to treat problems of the hair and scalp.
trigamist
A person who has three spouses simultaneously.
tritagonist (s) (noun), tritagonists (pl)
In ancient Greek drama, the third actor, whose part is usually that of the evil genius or as a promoter of the sufferings of the protagonist: In his lively readings of ancient Greek dramas, Dr. Cooper used a shrill voice when he represented the tritagonist talking.
tritheist (s) (noun), tritheists (pl)
A person who believes that the three persons of the Christian Trinity are three separate gods: Tritheists have a belief that the Father, Son, and Holy Spirit are three distinct deities, which is considered contrary to the established teachings of orthodox Christianity.