Pictured above is the longest word in the English language. It's a slang term for a disease incurred by inhaling silicone dioxide. Sam Kean has a story at NPR's website describing the difficult task of defining a "word" so that one may determine which is the longest.
For example, do the names for chemical chains count? Does a word have to be published to qualify? Should words intentionally created to be the longest be considered real words? Kean lists the six words that qualify under various criteria. Which do you think is the best case for the longest word?
Link via Kottke