i think its about a sickness or something... anyways i had to search it too: The longest words in Oxford Dictionaries Online are:

antidisestablishmentarianism-opposition to the disestablishment of the Church of England - 28 letters
floccinaucinihilipilification -the estimation of something as worthless - 29 letters
pneumonoultramicroscopicsilicovolcanoconiosis-a supposed lung disease - 45 letters

Answers

2014-01-29T15:56:52+08:00
It depends on the dictionary, but I think that pneumonoultramicroscopicsilicovolcanoconiosis is the longest English word ;)
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2014-01-29T17:59:15+08:00
Longest words in Oxford Dictionaries Online are:

antidisestablishmentarianism-opposition to the disestablishment of the Church of England - 28 letters
floccinaucinihilipilification -the estimation of something as worthless - 29 letters
pneumonoultramicroscopicsilicovolcanoconiosis-a supposed lung disease - 45 letters
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