A pandemic is an epidemic that spreads internationally. My friend said that COVID-19 is a global pandemic. Isn't saying that coronavirus is a pandemic already indicative that it is global? Is "global" redundant?
Not redundant. Every definition of pandemic that I’ve read specifies that the word is used when referring to widespread diseases and not just global ones. For example, see Wikipedia’s definition.
Disease travels a lot faster and further than it did before, because people do, so I’m not sure how many more non-global pandemics we will have. The Black Plague is a good example of a pandemic that was not global, due to the Americas not being known to Europe:
The Black Death was one of the most devastating pandemics in human history, resulting in the deaths of an estimated 75 to 200 million people in Eurasia and peaking in Eurasia from 1331 to 1353. Its migration followed the sea and land trading routes of the medieval world.
In my opinion, it is redundant but somewhat necessary to inform the general population. The word "pandemic" describes the outbreak of a disease which already has (or is very close to) affect every community in the world.
To understand the glossary better, you have to look at the endemic and epidemic as well. Endemic describes the outbreak of a disease inside a single community that can be a neighborhood, city, country, etc. Epidemic describes the widespread outbreak of a disease affecting multiple communities that can be multiple cities, provinces, countries, etc.
A pandemic is just an epidemic that has spread wide enough to affect (or potentially affect) every community in the world. So, if an epidemic has not reached a global level, it would still remain an epidemic and if you need to call an outbreak pandemic, it is a global event. Hence, "global" is redundant.
For instance, the Coronavirus outbreak was declared a pandemic by WHO only when there was a meaningful outbreak in all 5 continents.
However, since such technical medical words are not very meaningful to the population, calling pandemic a "global pandemic" is a necessary redundancy to inform the population about the magnitude of the disease that may endanger them.