-ist

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

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.
trivialist
tropist (s) (noun), tropists (pl)
Someone who deals in tropes.
tympanist, timpanist
Someone who plays the kettledrums and other percussion instruments in an orchestra.
typologist
ultraist
unilateralist
unionist
universalist
urinologist