The amount of work a person, a team, or a machine has to do — how much is on your plate. It is an uncountable-feeling noun that still takes a/an: a heavy workload, a light workload. The usual partners are heavy, increase, reduce, share, manage, and it is one of those calm office words that people reach for when they want to complain without sounding like they are complaining: instead of "I have too much work," you say "my workload has increased." That makes it safe to say to a boss. Teachers talk about student workload; hospitals talk about the doctors' workload; computer people also say workload for the amount of processing a server has to handle, which is the same idea moved to machines. The word says nothing about how hard the work is, only how much — a huge workload of easy tasks is still a huge workload.