I know this should be an easy question but in fact it's actually a mind boggling question.
Look, I was on the PC trying to type unforgiveness into a sentence; only to find out that the spellchecker marked the word as incorrect! Then I thought "maybe it's just the spellchecker making a mistake." But when I searched it up on dictionary.com it too couldn't find it!
I think it's quite weird. Most people use this word a lot and yet it isn't even in the dictionary. We even know the definition of the word and still it doesn't exist in any of our dictionaries! It's the first time I've ever seen a word that is used in many works of literature only to find out that "it's not a real" word.