Supercalifragilisticexpialidocious! Yeah. With over 30 letters and 14 syllables, it's the longest single word that I know. Say it just like you read it:
Super; Cali; fragil; istic; expee; ali; doch; is.
I know that that's a pretty bad way to show you guys, but it's what I've got. If you want a better one, go to this link. Dictionary.com actually has it listed as a real word, but their definition is kind of funny.
The word started out from a song from the original 1964 Disney film Mary Poppins. I find it somewhat amusing that Dictionary.com lists the definition as "a nonsense word used by children to express approval or to represent the longest word in English."
You can hear a portion of the whimsical song here:
It's a bit weird, though. I only know about this song because in first grade, my class had a set of ten-fifteen spelling words that we had to practice each day, then we would be tested on them on Friday. For the last week of the year, our teacher announced that we would only have one spelling word. We all got really exited and clapped and cheered... until we saw the word.
Honestly, I'm not even sure if it's a "real" word, but if the dictionary website, as well as others, give you the definition of it, I'm assuming that it is. Let me know what the longest word that you guys know is.