Pneumonoultramicroscopicsilicovolcanoconiosis- a
factitious word alleged to mean 'a lung disease caused by the inhalation of very fine silica dust causing inflammation in the lungs. it was coined to serve as the longest
English word and is the
longest word ever to appear in an
English language dictionary. This 45-letter word, referred to as
P45, first appeared in the 1939 supplement to the
Merriam-Webster New International Dictionary, Second Edition[3]. It is listed in the current edition of several dictionaries. A condition meeting the word's definition is normally called
silicosis.