Lets say you got a list named Words and a list UniqueWords, start a loop on Words, on each iteration you check if the list UniqueWords contains the iterated element, if so then continue, if not then add it to the UniqueWords. In the end you will have a list without duplicates. Another way you could do is a loop in a loop and instead of adding you'd remove it if it was found more than once :)
I bet there are far more efficient ways though.
