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

nonsexist (s) (noun), nonsexists (PL)
Someone who does not discriminate nor make decisions based on gender (masculine or feminine).
Someone who is versed or who specializes in noology.
A specialist in the classification of diseases.
One who studies senility; a gerontologist.
A collector of bank notes.
novelist (s) (nouns), novelists (pl)
A person who writes novels or stories in books about many subjects and people: Grace is a novelist who has been creating and publishing many fictions for several years.
nudist (s) (noun), nudists (pl)
Someone who prefers to go without clothes; especially, someone who spends time in communes or designated areas with others who feel the same way.
numerologist (s) (noun), numerologists (pl)
A believer or someone who practices the art of predicting the future based on mathematical quantities that are related to a person's birthday: Gerald, the numerologist, told Maurice that his book would be a successful publication and financially rewarding for him.
nutritionist (s) (noun), nutritionists (pl)
Someone who studies, or who is an expert, in the field of healthy eating: In a hospital, or nursing home, a nutritionist is a person who plans and/or formulates special meals for patients.

Nutritionists can help patients with special needs; such as, devising healthy diets to control allergies, health problems, a desire for increased energy, or weight changes.

Some nutritionists in private practices are well-trained, hold a degree, and are licensed; however, depending on state law, a person using the title may not be trained or licensed at all.

A person who has an abnormal preference for darkness or night.
obscurantist (s) (noun), obscurantists (pl)
1. Someone who is deliberately vague or unclear: Mr. White, the mayor, was accused of being a professional obscurantist because he refused to meet with the press and he denied public access to the city council meetings.
2. A person who is opposing or hindering the spread of new ideas and new social or political developments: Mr. Johnson, the prime minister of the country, was considered to be an obscurantist who was continually operating under a cloak of secrecy.
occultist (s) (noun), occultists (pl)
Someone who participates in secret, mysterious, and supernatural activities: As an occultist, Jack's mother was the leader in the rites of the organization with her fellow members.

An occultist is someone who practices any of the secret mystic arts; such as magic, Theosophy, mysticism, or spiritualism.

oceanologist (s) (noun), oceanologists (pl)
An individual who specializes in the scientific study of oceans: Tom, an oceanologist, did research on the life that inhabits the seas and the physical characteristics of the seas, including the depth and extent of sea waters, their movement and chemical makeup, and the topography and composition of the sea floors.