professional

noun

1. A person who belongs to a profession.
2. A person who earns their living from a specified activity.

   “My son, a Canada-based IT professional who often travels to Ukraine, told me about the exhilarating atmosphere on those Ukraine-bound trains, bringing home hundreds of the unwilling refugees, mostly women and children (including the babies, born in exile on the way to meet their Ukrainian fighter fathers for the first time). The difference between Ukrainian refugees and other reluctant exiles is that Ukrainians are desperate to return.”

3. (euphemistic)A prostitute.

   “There was this nice lady who flirted with me at the bar, but it turned out that she was a professional.”

4. A reputation known by name.
5. An expert.

   “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.”

6. One of four categories of sociologist propounded by Horowitz: a sociologist who is actively concerned with promoting the profession of sociology.

adj

1. Of, pertaining to, or in accordance with the (usually high) standards of a profession.

   “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.”

2. That is carried out for money, especially as a livelihood.
3. (broadly)Expert.