which one is the most complicate word in the english vocabulary?

Answer 1

If by complicated you mean longest, the winner is:

Pneumonoultramicroscopicsilicovolcanoconiosis

http://en.wikipedia.org/wiki/Longest_word_in_English

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Cheers,
Bruce

Answer 2

I can not type the full word, but it is the word for a distinct part of the dna. it is 1909 letters long.