The longest word starting with the letter P is Pneumonoultramicroscopicsilicovolcanoconiosis. It is also the longest word in the English language published in a dictionary. It refers to a lung disease.
Pulses
pensive
Pearl.
The opposite of ornate is plain.
A piste
Pneumonoultramicroscopicsilicovolcanoconiosis (also happens to be the longest word in the English language)
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.
The longest word starting with E is Electroencephalographically.
Scoop, Soup, and others, I'm not 100% sure about the rest though
Floccinaucinihilipilification is the longest word starting with F; it means the act of estimating something as worthless.
p-
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.
forethoughtfulness
Immunoelectrophoresis-- 21 letters
enormous
iufijifidafhudfhafa