The 45-letter lung disease is pneumonoultramicroscopicsilicovolcanoconiosis.
This incredibly long word refers to a lung disease contracted from the inhalation of very fine silica or quartz dust, especially that found in volcanoes; essentially, silicosis. As the reference states, "Pneumonoultramicroscopicsilicovolcanoconiosis is the longest word to be recognized by major english speaking dictionaries." This recognition is primarily because it's a real, although rare, condition.
Here's a breakdown for easier understanding:
- Pneumono-: Relating to the lungs
- Ultra-: Extremely
- Microscopic-: Extremely small, visible only with a microscope
- Silico-: Relating to silicon or silica
- Volcano-: Relating to a volcano
- Coni-: Relating to dust
- -osis: A disease or abnormal condition
Therefore, it describes a lung disease (pneumonosis) caused by the inhalation of very fine (ultramicroscopic) silica dust (silico) from volcanoes (volcano) causing a dusty (coni) condition (-osis).
