Methionylthreonylthreonylglutaminylalanyl...isoleucine. It has 189819 letters and the longest word in the world.
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.
One of the longest words starting with the letter "m" is "methionylthreonylthreonyl," which is a chemical term related to amino acids. However, in more general usage, "microphotolithography" is often cited as one of the longest words beginning with "m," referring to a technology used in semiconductor fabrication. Both words illustrate the complexity and specificity of language in different contexts.
Pneumonoultramicroscopicsilicovolcanoconiosis (also happens to be the longest word in the English language)
Extraterritoriality is the longest word in the English language beginning with "ex."
methionylglutaminylarginyltyrosylglutamylseryllleucylpheny
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.
forethoughtfulness
Immunoelectrophoresis-- 21 letters
enormous
iufijifidafhudfhafa
MEIOSIS is the longest word that can be made from those letters.