WTN- One has to try more attempts than the characters in this word to get exact pronunciation of this word "Pneumonoultramicroscopicsilicovolcanokoniosis’".  According to Oxford modern English this word is the longest word of the English.

The 45 character long word is a lung disease caused by inhaling very fine ash and sand dust.

While Pseudopseudohypoparathyroidism contains thirty letters and the second longest word in English.  This word also associated with medical condition of body that simulates the symptoms of the disorder in the blood. – Window To News