Supercalifragilisticexpialidocious (deep breath) is NOT the longest word in the English dictionary. 

It is Pneumonoultramicroscopicsilicovolcanoconiosis.

According to the Oxford English Dictionary, this 45-letter word is the scientific name for a lung disease caused by inhaling ash and dust. It’s a synonym for silicosis and was coined in 1035 to claim title of the longest English word, a jab at complicated medical terms. 

But wait… There’s an even LONGER word, although not officially included in the dictionary. 

The full chemical name for the human protein titin is Methionylthreonylthreonylglutaminyl… the word goes on, with a total of 189,819 letters, taking over three and a half hours to pronounce!

If you have a few hours to spare, you can watch it being read HERE.