It is any system that conveys fluids for a wide range of applications.
Plumbing uses pipes, valves, plumbing fixtures, tanks, and other apparatuses to convey fluids.
And heating and cooling (HVAC), waste removal, and potable water delivery are among the most common uses for plumbing.
But it is not limited to these applications.
The word derives from the Latin for lead, as the first effective pipe use in the Roman era was lead pipes.
And in the developing world, plumbing infrastructure is critical to public health and sanitation.
Boilermakers and pipefitters are not plumbers although they work with the pipe as part of their trade.
And their work can include some plumbing.