The longest word in the world contains 189,819 letters, and it takes approximately three hours to pronounce it. "Pneumonoultramicroscopicsilicovolcanoconiosis" has 45 letters. It is the undisputed longest word as of 2015, and it refers to an inflammation in the lungs caused by inhaling silica dust.
The Digital Spy website provides a video of a man pronouncing the 189,819 lettered word. The video is more than three hours long, and the website displays the word beneath it. Other special words occasionally arise to make a claim to long-word fame, such as "supercalifragilisticexpialidocious," made famous by a song in the 1964 "Mary Poppins" movie.