Which is the longest word in English?

English has been one of the most peculiar language in the world. Not only we are being slapped with different tone and pronunciation for almost similar style of writing, for example: tough, though, rough, etc. The language is also a surprise as you can find the longest word in English accounts for more than 45 letters! 

The longest word in English is  

PNEUMONOULTRAMICROSCOPICSILICOVOLCANOCONIOSIS 

but wait, this particularly long word also has the other version of spelling (sigh, talks about headache!).

It can also be spelled

PNEUMONOULTRAMICROSCOPICSILICOVOLCANOKONIOSIS) 

which carries the meaning of

"a lung disease caused by breathing in particles of siliceous volcanic dust".

 This is the longest word in any English dictionary and worry not, you might not be using this word sooner or later unless you are a doctor or trying to explain to someone having this kind of disease.