Longest Word

The longest word in the English languages describes the largest protein known. It contains 189819 letters. It is usually shortened to "Titin" but sometimes is also shortened to Methionylthreonylthreonyl...isoleucine. The Longest Word. (too long to put on this page)

You could argue, however, that it is actually a medical word, not a real word in the dictionary. So, to make this page really list the longest word ever, here is the largest word in the English language in the dictionary:

Pneumonoultramicroscopicsilicovolcanoconiosis.