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

Anyone who denies the existence of demons or the Devil.
adiabolist (s) (noun), adiabolists (pl)
A person who denys the existence of the Devil.
Adventist (s) (noun), Adventists (pl)
A member of the Seventh-day Adventist Church; a person who believes in the Second Advent: Susan was an Adventist who had faith in the imminent advent of Christ.
aerobiologist (s) (noun), aerobiologists (pl)
Someone who specializes in the study of airborne microorganisms or spores: Jack's dad was an aerobiologist who studied the effects of viruses, pollen, and pollutants that were transported by air currents.
aerologist (s) (noun), aerologists (pl)
A specialist in the branch of meteorology concerned with the study of air, especially in the upper atmosphere: Linda's father was an aerologist and did research on total atmospheric meteorology as opposed to surface-based applications.
aeromantist (s) (noun), aeromantists (pl)
An individual who foretells the future by examining air or atmospheric conditions: An aeromantist can be a weather forecaster.or a person who believes in being able to interpret a person's future by observing the characteristics in the atmosphere.
An unmarried person.
agathist (s) (noun), agathists (pl)
An adherent of the belief of "agathism": Jane's mother was an agathist and thought that "all things tend towards ultimate good".

Grace's aunt said that the world and things in general were heading for the better, therefore in things that other people she knew regarded as evil or tragic, includ.ing virulent diseases, calamitous earthquakes, or wars. She was an agathist who could find some ultimate purpose for good.

The optimist sees the present as pretty much for the "best". The agathist is less content with the present, thinks things are inevitably tending towards good despite the bad situations which precede the ultimate results.

agonist (s) (noun), agonists (pl)
1. In physiology, a muscle whose contraction is directly responsible for the movement of a part of the body: In his biology class, Jeff learned that the agonist in bending the elbow was the biceps!
2. A contender for prizes in competitions; a protagonist: Jack was an agonist who took part in the sports contest at school.

An agonist can be an individual who has a leading role in a drama presentation, or is the principal character in a story.

agricolist (s) (noun), agricolists (pl)
A cultivator of the soil; an agriculturist: Mary's father was an experienced agricolist who gave advice to other farmers regarding their soil and the cultivation of crops.
agriculturalist (s) (noun), agriculturalists (pl)
Someone who is engaged in farming: An agriculturalist is also concerned with the science, art, and business of cultivating soil, producing crops, and raising livestock.
Whoever could make two ears of corn . . . grow upon a spot of ground where only one grew before, would deserve better of mankind . . . than the whole race of politicians put together.
—Jonathan Swift (1667-1745)
agriologist (s) (noun), agriologists (pl)
Someone who is versed in the history and customs of primitive or uncivilized peoples: Mary's mother was an agriologist who was an expert in the comparison of prinitve, illiterate, and "savage" cultures.
agrizoiatrist (s) (noun), agrizoiatrists (pl)
A veterinarian who tends to or is concerned with wild animals: Mr. Dawson worked as an agrizoiatrist with the rangers of the large forest and cared for the deer, bears, rabbits, and wild boars.
agrobiologist (s) (noun), agrobiologists (pl)
An expert in the field of plant nutrition and growth: An agrobiologist is a specialist in the line of bacteria and microorganisms in soil regarding the growth of crops and the feeding of domestic animals.
agroecologist (s) (noun), agroecologists (pl)
An expert in or a student of the design, development, and management of sustainable agricultural systems: An agroecologist studies the applications of ecological principles while considering existing social, cultural, and economic factors of farming communities.