In photographic equipmet or supplies, the term"PROFESSIONAL" MIGHT be indicative of the product being intended for "heavy duty" use in that it is sturdily built, will stand up well in constant service, and is capable, in the right hands, to delver very high quality imagery for discriminating users who's work subject to critical scrutiny by expert clients OR NOT! It also MAY be marketing hype.

Not too many cameras and lenses are actually designated or branded as such. Certain makes and models may be more popular and preferred by professionals. Obviously, the are not restricted to non-professionals. If you can afford them you can buy them. They are not surgical instruments or heavy warfare armaments or explosives.

Funny- the last camera I can think of that actually had the word "professional" in it official name and emblazoned on the camera itself, was back in 1957 when Mamiya introduced its Mamiyaflex Professionl C. It was the first twin lens reflex camera with interchangeable lenses. It was competition with the Rolleiflex which had a fixed lens but automatic film advance and shutter cocking and some Rollei models had a on-board exposure meters, automatic parallax correction, a rapid film advance crank, an add on prism finder and and rangefinder accessories- all big deals at the time. The Mamiyaflex had their lens selection but, at the time, there was only a rather dark accessory mirror finder with a reversed image, no parallax correction- there was a kinda strange outboard accessory to use the camera at 7 inches from the subject- it did have built in bellows. The focus knob and the manual film advance knob (no crank) was on the wrong side of the camera (as per Rollei users) and the shutter had to be cocked manually as well. The lenses were OK but there weren't Schneider or Zeiss. Oh- and there was no double exposure prevention. Thing was, you had to be a pretty savvy pro to use the thing- it was a bit o a clunker as compared to the rather sleek and popular Rolleiflex. After a while it was improved and did became one of the industrie's workhorse cameras.

Funny again- the Speed Graphic, the all time king of the PRESS cameras was never branded as a PRESS camera. Mamiya to the rescue again! They named their medium format rangefinder camer the PRESS 23. The Linhof folks had a PRESS 70 and Schneider branded one of their lens lines as PRESS Xenotar.

I guess the words "PRESS and PROFESSIONAL" hold certain amount of prestige?

Then there were "PROFESSIONAL" films. Kodak claimed that there professional color negative films, such as Varicolor and Portra were aged in a certain way to maxamize color fidelity but had shorter shelf lives and required prompt processing after exposure- no problem for pros. They also had a retouching surface on the base. They claimed there pro black and white films had retouching surfaces where as the others did not. Funny again, Kodacolr film, which was intended for amateur use had finer grain, more neutral color, more latitude and coud be used in hazardous tropical conditions. Verichrome film, their archetype amateur product had finer grain, better tonal gradations and more latitude that any of their pro films.

Nowadays the word "DIGITAL" is bandied about. I have seen ads for "digital' filters, cases, tripods and stuff that has nothing to do with digital technology.

It could be that pro photographers are not licensed or have certificates of achievment, but pro equipment is distinguishable from more "ordinary" equipment.

"Pro" equipment is built more ruggedly to withstand harder usage. It is built with more precision parts and designed so those parts will last longer (and can be replaced). "Pro" lenses are made to more exacting standards and in general have better performance in terms of corner sharpness and various distortions and aberrations.

"Pro" photographers (however you define them) use all sorts of equipment, both pro-level and consumer-level, and probably other equipment that isn't amenable to classification. Pro equipment can be used by anyone. For example I use pro-level camera bodies and lenses. I use Adobe software, which could be considered pro-level in my opinion. But I'm not a pro. I take my share (or maybe more) of useless photos. I don't make any money off of my hobby. But I enjoy the technological aspects of the pro-level gear.

The discussion of how to define a pro photographer comes up a half dozen times a year on all the forums I participate in. There are twice as many definitions of pro photographer as there are posters in the forums. I consider this a question without an answer, and moreover, a distinction that is unimportant.