a disease that killed an extremely large number of people in Europe and Asia in the 14th century, usually thought to be a form of bubonic plague, a very infectious disease caused by bacteria spread mainly by fleas (=small insects that bite) on rats or other animals, that causes swelling, fever, and usually death in humans

In the 14th century, crop failures, war, and the onset of the Black Death all reduced the population by between a half and a third.

In the period following the Black Death there was an acute shortage of labour.