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Terramoto vs. terremoto vs. sismo

Word practice demo
In Portuguese, the words terramoto, terremoto, and sismo are all used to refer to earthquakes, but they vary in terms of usage, regional preference, and formality. Understanding their differences helps clarify when and where to use each term appropriately.

Terramoto

B1
Terramoto is an older and more traditional form of the word terremoto. It is predominantly used in European Portuguese (Portugal). Although still understood in most contexts, its usage has declined in favor of terremoto.
O terramoto de Lisboa em 1755 devastou a cidade.
(The Lisbon earthquake of 1755 devastated the city.)
Depois do terramoto, muitos edifícios ficaram destruídos.
(After the earthquake, many buildings were destroyed.)

Terremoto

B1
Terremoto is the most commonly used term in Brazilian Portuguese and is also perfectly understood in Portugal. It comes from the Latin terrae motus (movement of the earth) and has become the more modern and widely preferred term in both written and spoken contexts, especially in Brazil.
O terremoto no Chile foi um dos mais fortes da história.
(The earthquake in Chile was one of the strongest in history.)
Durante o terremoto, a população foi evacuada das áreas perigosas.
(During the earthquake, the population was evacuated from dangerous areas.)

Sismo

B2
Sismo is a more scientific and formal term for an earthquake. It is frequently used in academic, geological, and technical contexts. It is also more commonly encountered in European Portuguese compared to Brazilian Portuguese.
Os sismos são estudados pela sismologia, uma área da geofísica.
(Earthquakes are studied by seismology, a field of geophysics.)
Houve um pequeno sismo na região, mas sem danos significativos.
(There was a small earthquake in the region, but without significant damage.)

Summary

The terms terramoto, terremoto, and sismo all describe earthquakes in Portuguese, but they differ in use and context. Terramoto is older and more common in Portugal but falling out of usage. Terremoto is modern and widely used in Brazil and also understood globally. Sismo is formal and scientific, often used in technical or academic discussions, particularly in European Portuguese.