demethylchlortetracycline
dichlorodifluoromethanes (24 letters)
Overenthusiastically or Overapprehensiveness Both are 20 letters long :D
The longest word starting with E is Electroencephalographically.
Floccinaucinihilipilification is the longest word starting with F; it means the act of estimating something as worthless.
Pneumonoultramicroscopicsilicovolcanoconiosis (also happens to be the longest word in the English language)
dichlorodifluoromethanes (24 letters)
Overenthusiastically or Overapprehensiveness Both are 20 letters long :D
The longest word starting with E is Electroencephalographically.
Floccinaucinihilipilification is the longest word starting with F; it means the act of estimating something as worthless.
Pneumonoultramicroscopicsilicovolcanoconiosis (also happens to be the longest word in the English language)
Extraterritoriality is the longest word in the English language beginning with "ex."
Methionylthreonylthreonylglutaminylalanyl...isoleucine. It has 189819 letters and the longest word in the world.
The longest word starting with a "P" is pneumonoultramicroscopicsilicovolcanoconiosis, which has 45 letters and is in the Guinness Book of Records. It was, however, coined for the specific purpose of becoming the longest word, and is not a specifically recognized form of silicosis.
Including the letters d, b, f, the longest word might be defibrillation.
forethoughtfulness
Immunoelectrophoresis-- 21 letters
enormous