Pandemic is observed in the Greek pandēmía, its breakdown allows the identification of the elements pan-, which refers to everything or all, taking its root from the Indo-European *pan-, again, indicating wholeness, and dēmos, which interprets the idea of community, village, or group of people, related to the Indo-European word *da-mo-, meaning division, linked to *da, as to divide, finally having the suffix -ic, based on Greek -ía, acting to form the adjective as well as the noun sense of the word.
On the other hand, unlike “pandemic”, the term epidemic can be found in the medieval Latin epidemia, from the Greek epidēmía, with the prefix epi-, which can be interpreted as over or on top (in this case, referring to the population), and endemic, seen in the French endémie, from the Greek éndēmos, outlined by the prefix en-, which reflects the idea of an intense reiteration event that ocurrs over a region.
Therefore, the significance of a pandemic indicates the propagation and development of diseases, including the agent that causes them, with the ability to spread among several countries or to deeply impact a region or a whole community. This is how we arrive at the WHO’s statement declaring COVID-19 as a pandemic, once it was born in a city in China in mid-November 2019 and spreading to the rest of the world forcing the implementation of extreme measures. Recent episodes include Ebola (which emerged in 1976 and reappeared in 2014), Influenza A (which appeared in 2009), same way as smallpox, which was eradicated in 1979, being the largest pandemic in human history responsible for more than 300 million deaths.
In conclusion, there are three progressive steps differentiated at the linguistic level by the prefix, according to the level of impact and spread of conditions: pandemic has a scope that exceeds the regional limits where the disease originates, while epidemic contains the problem in one specific area, and endemic focuses on a disease that tends to be recurrent in a population given the socio-cultural conditions and geographical location.
Likewise, the field dedicated to study these agents in depth, accompanying the propagation activity as well as establishing factors and effects, is called epidemiology, combining the elements of the Greek epidēmía and the suffix -logy, which refers to logos, attaching a science or analysis title.