3 Answers

Someone who can sort out a problem, for you without fear or favour,and leave you relaxed with a problem resolved,

A medical practitioner who deals only with a particular class of diseases,  conditions, A person who devotes himself or herself to one subject or to one particular branch of a subject.

(sp?sh'?-l?st)
n.
One who is devoted to a particular occupation or branch of study or research: "Specialists . . . tend to think in grooves" (Elaine Morgan).
A physician whose practice is limited to a particular branch of medicine or surgery, especially one who is certified by a board of physicians: a specialist in oncology.
Any of several noncommissioned ranks in the U.S. Army that correspond to that of corporal through sergeant first class.

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