At the end of the day there's more than one way to interpret the adjective 'professional' so it will simply come down to how someone wishes to portray themselves if they call themselves a pro.
It can either be taken to differentiate that you're trading as a profession i.e. your main source of income, much the same as you'd separate professional footballers and amateur footballers. Lots of people play football not many are pro's, not many people are plumbers so they rarely need to define themselves as a pro plumber/electrician etc. Or you use the adjective professional to imply you've excelled at trading, extremely competent and a cut above the crowd .
Trader Pat wrote: ↑Thu Dec 06, 2018 7:09 pm.............but in my experience if you tell everyone who asks that you're a trader most of them will assume you're a just a gambler anyway so it wastes a lot of time to tell them otherwise.
I gave up trying to explain to people what I did a long time ago, always seem to be more trouble than it's worth especially if they want you to teach them I just say I work in an office if anyone asks usually it's less hassle.