Pneumonoultramicroscopicsilicovolcanoconiosis: The World's Longest Word Explained

Pneumonoultramicroscopicsilicovolcanoconiosis (45 letters) is the longest word in major English dictionaries. It was coined in 1935 by Everett Smith, president of the National Puzzlers' League, as a tongue-in-cheek term for a lung disease caused by inhaling very fine silica dust (silica dust from volcanoes).

Medically, the condition is simply silicosis – a pneumoconiosis from crystalline silica exposure. No patient has ever been diagnosed with "pneumonoultramicroscopicsilicovolcanoconiosis" as a distinct entity; it is a linguistic curiosity.