So is a "hobby" something pleasurable that you do that does not earn you any money? Riding bicycles isn't a hobby; I rode to two entire seasons of reality TV on my bicycle. Motorcycling isn't a hobby; the only thing better than ripping up the PCH to Ventura on a shiny Saturday morning on a motorcycle is being paid to rip up the PCH to Ventura. Photography is now a hobby but back before digital it contributed substantially to my income. Audio hasn't been a hobby for a couple decades but it started that way. Writing hasn't been a hobby for ten years or more but it started that way. I guess nobody's paid me for the fish tank but I toss 20 or 30 of these down the drain every week. Nobody pays me to fly tiny helicopters but if you don't think I've looked seriously at quadcopters capable of lofting my buddy's Red Epic you're sorely mistaken. One of the best decisions I ever made was creating as much overlap as possible between "things I do for fun" and "things I do for money."