Question: what is the longest english word in the dictionary?
Answer: pneumonoultramicroscopicsilicovolcanoconiosis, Methionylglutaminylarginyltyrosylglutamyl ... serine, Pneumonoultramicroscopicsilicovolcanoconiosis

The longest word in any of the major English language dictionaries is pneumonoultramicroscopicsilicovolcanoconiosis, a word that refers to a lung disease contracted from the inhalation of very fine silica particles, specifically from a volcano; medically, it is the same as silicosis.  The word was deliberately coined to be the longest word in English, and has since been used in a close approximation of its originally intended meaning, lending at least some degree of validity to its claim.