Which is the longest word in English?

Pneumonoultramicroscopicsilicovolcanoconiosis was invented in 1935 by Everett Smith, president of the National Puzzlers’ League, deliberately to be the longest word. It still made it into the Oxford English Dictionary and describes a lung disease similar to silicosis. The full chemical name of the protein titin has about 189,819 letters and would take hours to say, but it is not considered a real dictionary word. Antidisestablishmentarianism, at 28 letters, is famous as the longest non-technical word, meaning opposition to removing the Church of England’s official status. Supercalifragilisticexpialidocious, 34 letters, was popularised by the 1964 film Mary Poppins.