HAECCEITY
quiddity, haecceity
(noun) the essence that makes something the kind of thing it is and makes it different from any other
Source: WordNet® 3.1
Etymology
Noun
haecceity (countable and uncountable, plural haecceities)
(philosophy) The essence of a particular thing that gives it its unique particularity; those qualities that make an individual this specific individual and not some other.
Synonyms
• thisness
Source: Wiktionary
Hæc*ce`i*ty, Etym: [L. hæcce this.] (Logic)
Definition: Literally, this-ness. A scholastic term to express
individuality or singleness; as, this book.
Source: Webster’s Unabridged Dictionary 1913 Edition