Key Terms You Must Know

📖 Key Terms You Must Know

Black Death (1348-1350)

A devastating epidemic that killed approximately 30-50% of England's population (roughly 2 million people) and up to one-third of Europe's population. It was caused by the bacterium Yersinia pestis, spread by fleas on rats, though medieval people did not know this. It arrived in England in 1348, probably through the port of Weymouth, and spread to most of England by 1350. The name "Black Death" refers to the black swellings (buboes) that developed in victims' lymph nodes.

Bubonic plague

The most common form of the Black Death. Named after "buboes" — painful black swellings (infected lymph nodes) that appeared in the armpits, groin, and neck. Caused by flea bites transferring the bacteria into the bloodstream. Killed approximately 30-60% of those infected within 3-5 days. The buboes turned black and burst, which is how the disease got its name.

Pneumonic plague

A more deadly form of the Black Death, spreading through the air when infected people coughed or sneezed. Affected the lungs rather than lymph nodes. Almost always fatal. This form enabled the disease to spread even faster because no rat or flea was required — direct human contact was sufficient. This is why plague could spread through sealed houses and religious gatherings.

Miasma theory

The dominant explanation for the Black Death: poisonous "bad air" rising from rotting matter. This belief led to responses such as carrying posies of flowers, burning herbs and bonfires, and avoiding bad smells. It was completely wrong about the cause, which meant all responses based on it were ineffective. Doctors who wore "beak" masks filled with herbs believed they were filtering out miasma — in fact, the masks also incidentally reduced some droplet spread, a benefit they did not intend or understand.

Flagellants

Groups of people (mainly in continental Europe) who whipped themselves publicly as an act of penance, believing that by punishing themselves they could appease God and end the plague. Their processions from town to town actually helped spread the disease across large distances.

Quarantine

Isolation of the sick to prevent disease spreading. Derived from the Italian "quarantina" meaning 40 days. Some towns, notably Milan, sealed infected houses immediately. This was the only medieval response that genuinely reduced the spread — not because people understood infection routes, but because it accidentally prevented infected fleas from moving to new hosts. Quarantine is the one medieval practice still used today.