Which is the Longest Word in English ?

Recently  a man named Dmitry Glubovskyi tried to pronounce a "word " having  189,819 letters which is considered by some as the longest word in English. He took around 3 hours 33 minutes 23 seconds to pronounce it. The "word" is the chemical name of  'TITIN'  which 


is the largest known protein in the world.  However, not all consider 'TITIN' chemical name as a "word".  According to Oxford Dictionaries Online, chemical names are not "genuine words in the sense of meaningful items of vocabulary". 

The longest "articial" word in Oxford Dictionary is 45-letter word, pneumonoultramicroscopicsilicovolcanoconiosis which is said to mean a lung disease caused by inhaling very fine ash and sand dust. This word was invented in 1935 by Everett M. Smith, president of the National Puzzlers' League, at its annual meeting.According to Wikipedia, the 45-letter word was coined to serve as the longest English word and is the longest word ever to appear in an English language dictionary.