Brain Game: Short Spell #7
By BY

It's time for a new Wednesday Wordplay challenge here at the mentalfloss.com Brain Game. Good luck!
ONE of the four words in the following list is misspelled. Identify the culprit:
IMAGINARY INCIDENTALLY INDISPENSIBLE IRRELEVANT
Here is the ANSWER.
THE ANSWER:
The misspelled word is INDISPENSIBLE.
The proper spelling is INDISPENSABLE.
Thanks for playing!