I was under the impression that the longest word in English was "encyclopedia" until my fifth grade.But it was only a few hours back that I found this word in the Oxford dictionary.

The medical term for a lung disease caused due to excessive inhalation of silica, Pneumonoultramicroscopicsilicovolcanoconiosis, is reportedly the longest word in the language.The word consisting of 45 letters is the longest word ever to appear in an English language dictionary.