identity vs unicity

identity

noun
  • Sameness, identicalness; the quality or fact of (several specified things) being the same. 

  • An element of an algebraic structure which, when applied to another element under an operation in that structure, yields this second element. 

  • A well-known or famous person. 

  • A name or persona—a mask or appearance one presents to the world—by which one is known. 

  • The difference or character that marks off an individual or collective from the rest of the same kind; selfhood; the sense of who something or someone or oneself is, or the recurring characteristics that enable the recognition of such an individual or group by others or themself. 

  • An equation which always holds true regardless of the choice of input variables. 

  • Any function which maps all elements of its domain to themselves. 

unicity

noun
  • The state or quality of being unique or one of a kind. 

  • The fact of being united as a whole. 

How often have the words identity and unicity occurred in a corpus of books? (source: Google Ngram Viewer )