Explanandum and explanans are concepts used in the philosophy of science. An explanandum is something that needs to be explained. For instance, someone asks why there's smoke on the horizon, they're offering an explanandum and seeking an explanation. They are seeking an explanans, or set of claims that will explain the explanandum. Continuing the example, if 'There is smoke on the horizon' is an explanandum, then 'There is a fire over at the Old Mill' would be one possible explanans. Hempel and… (More on Explanandum)