Worlds longest word

The longest word in the English language, according to the Oxford English Dictionary, is pneumonoultramicroscopicsilicovolcanoconiosis.

The only other word with the same amount of letters is pneumonoultramicroscopicsilicovolcanoconioses, its plural.

The longest place-name still in use is a New Zealand hill, Taumatawhakatangihangakoauauotamateaturipukakapikimaungahoronukupokaiwenuakitnatahu.