What 45-letter word names a lung disease caused by inhaling very fine silica dust?

The 45-letter word for a lung disease associated with inhaling very fine silica dust is pneumonoultramicroscopicsilicovolcanoconiosis. Its parts point toward its intended meaning: "pneumono" relates to the lungs, "ultramicroscopic" to extremely small particles, "silico" to silica, "volcano" to volcanic material, and "-coniosis" to a dust-related condition.

The word is famous partly because it was deliberately coined in 1935 by Everett M. Smith, then president of the National Puzzlers' League, as an exceptionally long English word. It appeared in print that year and later entered a 1939 supplement to the Merriam-Webster New International Dictionary.

There is an important medical nuance. The word is often treated as a synonym for silicosis, a real occupational lung disease caused by inhaling crystalline silica dust. However, pneumonoultramicroscopicsilicovolcanoconiosis was an artificial term, and evidence for a distinct disease caused specifically by volcanic silica is limited. In ordinary quizzes, the long word remains the canonical answer.