A person who is motivated by personal enjoyment; a hedonist.
A person engaged in an activity for the pleasure of it.
Someone who is an expert in, or devoted to, some specific branch of study or research.
A stenotopic species.
A physician whose practice is limited to a particular branch of medicine or surgery.
Any of several non-commissioned ranks corresponding to that of corporal.
An organism that is specialized for a particular environment.
Specialised, involving detailed knowledge of a restricted topic.