Etimology
From Middle English professhennalle, professhynalle; equivalent to profession + -al.
noun
professional (plural professionals)
A person who belongs to a profession.
A person who earns their living from a specified activity.
(euphemistic) A prostitute.
A reputation known by name.
An expert.
One of four categories of sociologist propounded by Horowitz: a sociologist who is actively concerned with promoting the profession of sociology.
Examples
There was this nice lady who flirted with me at the bar, but it turned out that she was a professional.
I have learned that there is a person attached to a golf club called a professional. Find out who fills that post at the Green Meadow Club; […] invite the professional, urgently, to dine with us this evening.
adjective
professional (comparative more professional, superlative most professional)
Of, pertaining to, or in accordance with the (usually high) standards of a profession.
That is carried out for money, especially as a livelihood.
(by extension) Expert.
Examples
His forefathers had been, as a rule, professional men—physicians and lawyers; his grandfather died under the walls of Chapultepec Castle while twisting a tourniquet for a cursing dragoon; an uncle remained indefinitely at Malvern Hill; […].
The little green men were clearly professional soldiers by their bearing, carried Russian weapons, and wore Russian combat fatigues, but they had no identifying insignia. Vladimir Putin originally denied they were Russian soldiers; that April, he confirmed they were.