-ist
* Dentist: A practitioner of dentistry.
* Artist: A practitioner of art.
* Pianist: A performer of piano music.
* Scientist: A practitioner of science.
* Analyst: A provider of analysis services.
-ian
* Physician: A practitioner of medicine.
* Technician: A provider of technical services.
* Librarian: A practitioner of library science.
* Musician: A performer of music.
* Historian: A practitioner of history.
-er
* Teacher: A provider of education.
* Writer: A practitioner of writing.
* Singer: A performer of music.
* Baker: A provider of baked goods.
* Builder: A provider of construction services.
-or
* Actor: A performer in theater, film, or television.
* Instructor: A provider of instruction.
* Operator: A provider of services or a person who operates equipment.
* Supervisor: A provider of oversight or direction.
* Evaluator: A provider of assessment or evaluation.
-ologist
* Cardiologist: A specialist in the heart.
* Psychologist: A specialist in the mind.
* Biologist: A specialist in living organisms.
* Geologist: A specialist in the Earth.
* Archaeologist: A specialist in ancient cultures.
-iatrist
* Psychiatrist: A specialist in mental health.
* Pediatrician: A specialist in children's health.
* Geriatrician: A specialist in the health of older adults.
Other suffixes
* -therapist: A provider of therapy, such as a physical therapist or occupational therapist.
* -ician: A specialist in a particular field, such as a physician or electrician.
It's important to note that these suffixes are not always used consistently. Some words may have multiple suffixes that indicate the same thing, and some fields may use different suffixes to denote practitioners.