Pneumonoultramicroscopicsilicovolcanoconiosis

Most of the longest words written here are not English, they came from Latin and Greek actually or they are terminologies from the field of medicine. The longest English word should be, " Autobiography". :)

Easy the answer should be "smile" becoz there is a " mile" in "smile"

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Pneumonoultramicroscopicsilicovolcanoconiosis (45 letters) - a factitious word alleged to mean a lung disease caused by the inhalation of very fine silica dust, causing inflammation in the lungs. This is the longest word you can find in Oxford Dictionary to date.