indicating a person skilled or involved in a branch of study denoted by a noun ending in -logy (such as biologist corresponding to Biology).
Logist
-ologist means the person who studies.
The word 'dermatology', recorded in 1819, comes from the Greek derma, meaning skin, leather, or hide, plus the Greek suffix -logy, meaning science (of) or branch of learning or knowledge.The term 'dermatologist' comes into English from the same roots as above, with the suffix -logist, meaning practitioner of, or expert, or learned, in, added in 1861.
anesthesiologistanthropologistanthologistarchaeologistaudiologistastrologistbiologistcardiologistcosmetologistdermatologistecologistendocrinologistentomologistetymologistgastroenterologistgemologistgenealogistgynecologisteconomistgeologistgerontologisthematologistmonologistmycologistmeteorologistmythologistnumerologistneurologistoncologistontologistophthalmologistotolaryngologistpaleontologistpetrologisypathologistparasitologistpharmacologistpetrologistparasitologistpenologistradiologistsociologistseismologisttoxicologistufologisturologistzoologist
The suffix "-er" often means "one who does" or "one who performs the action." For example, a baker is one who bakes, a singer is one who sings, and a writer is one who writes.
Podologist pod/o- (Foot) -logist (one who studies)
Other than saying the person is a "specialist in..." or a "... major" (if in college), there's the use of the suffix "-logist" or "-ologist" for experts/scholars in particular fields: antropologist, paleontologist, mineralogist, theologist, meteorologist, biologist, bacteriologist... "TheEnglish suffix -ology or -logydenotes a field of study or academicdiscipline, and -ologist describes a person who studies that field. (source: http://en.wikipedia.org/wiki/List_of_ologies#List_of_-ologies)
A person who specializes in a particular field of science or study.
M. S. Wingersky has written: 'Logist user's guide'
A psychologist is a professional who studies and explains human behavior by conducting research, applying theories, and utilizing various assessment techniques. Psychiatrists, on the other hand, are medical doctors who can prescribe medication to treat mental health disorders in addition to providing therapy.
Neglectful combines "neglect" with the suffix "-ful".
The suffix of "undoing" is "-ing."