The word "quiddity" is a noun. An example of a sentence using the word would be: The true quiddity of the organization is becoming apparent.

Your quiddity is what makes you a unique individual.

Every person and every thing has a certain quiddity, an essence that makes it what it is.

the absolute extension of a term and concept is the sum total of the subjects of the actual subjects as well as the possible-whose quiddity (essence or nature) is signified by the term and concept.

They are all words that mean the opposite of themselves.

Example: Cleave means both to adhere to, and to split.

However, at least 'resign' is not homonymically accurate, as the meaning 'to surrender' is pronounced with a z, and resign 'to sign/issue again', is pronounced with an s.

Written, however, they do look the same.

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 1 words with the pattern --I-DI-Y. That is, eight letter words with 3rd letter I and 5th letter D and 6th letter I and 8th letter Y. In alphabetical order, they are:

quiddity