A pandemic (from Greek πᾶν pan "all" and δῆμος demos "people") is a disease epidemic that has spread across a large region; for instance multiple continents, or worldwide.
A widespread endemic disease that is stable in terms of how many people are getting sick from it is not a pandemic. Further, flu pandemics generally exclude recurrences of seasonal flu. Throughout history, there have been a number of pandemics, such as smallpox and tuberculosis. One of the most devastating pandemics was the Black Death, which killed an estimated 75–200 million people in the 14th century. The current pandemics are HIV/AIDS and coronavirus disease 2019 (COVID-19). Other recent pandemics include the 1918 influenza pandemic (Spanish flu) and the 2009 flu pandemic (H1N1).