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

Someone who uses a particular form of expression, word, phrase, expression, or idiom.
Someone who studies words.
luminologist (s) (noun), luminologists (pl)
1. Someone who studies the shimmering or glowing phenomena of lambency in living organisms: The Marine University hired Dr. Lawson, a renown luminologist, to chair the department which studied the underwater plant and animal life which produce a vivid luster.
2. A person who is versed in the study of books with colored illustrations: As a result of her artistic abilities and specialization in ancient manuscripts, Julie was hired by the library as a luminologist to catalogue and repair the illuminations in the manuscript collection.
lycanthropist (s) (noun), lycanthropists (pl)
Someone who is affected by the mental disease that involves thinking that he or she is a horse.
macrologist (s) (noun), macrologists (pl)
A dull conversationalist; usually, someone who is often at parties or other social gatherings.
1. A practitioner of maieutics.
2. An obstetrician.
A specialist in malacology.
One who is versed in malacotomy.
manakophilist (s) (noun), manakophilists (pl)
One who collects almanacs: Mr. Smith, a manakophilist, loved his old yearbooks and spent lots of time going through all the photos and information about his old school and town.
manicurist (s) (noun), manicurists (pl)
1. Usually a beautician or someone who specializes in giving treatment of the fingernails; including, shaping and polishing: There are people who go to manicurists regularly for treatment of their fingernails and, sometimes, even for other conditions of their hands.

Someone once wrote that we should remember that only manicurists are literally making money "hand over fists".

2. Etymology: "a person who professionally treats hands and fingernails" which came from French manicure; literally, "the care of the hands"; from Latin manus, "hand" + cura, "care, treatment".
Someone who tells fortunes.
marmorophilist (s) (noun), marmorophilists (pl)
One who collects marbles: Ever since Joe was a little boy, Joe loved marbles and had a whole drawer in his cabinet full of them. Once ever month he got together with other marmorophilists to compare them and trade.
martyrologist (s) (noun), martyrologists (pl)
1. A writer of martyrology.
2. An historian of martyrs.
3. Someone who specializes in the accounts of the lives and manners of the deaths of martyrs.
4. A writer of or a specialist in martyrology.
1. A person who is markedly more concerned with material things than with spiritual, intellectual, or cultural values.
2. Someone who denies the existence of spiritual substances, and maintains that the soul of man is the result of a particular organization of matter in the body.