-ist

a person who studies or practices a particular discipline;

a person who uses a device of some kind;

one who engages in a particular type of activity;

one who suffers from a specific condition or syndrome

one who subscribes to a particular theological doctrine or religious denomination;

one who has a certain ideology or set of beliefs;

one who owns or manages something;

a person who holds bigoted, partial views with respect to a particular matter.

a person who speaks or specializes in a (usually constructed) language.