Pronunciation: (kon-kôr'dns, kun-),[key] —n. 1. agreement; concord; harmony: the concordance of the membership. 2. an alphabetical index of the principal words of a book, as of the Bible, with a reference to the passage in which each occurs.
3. an alphabetical index of subjects or topics.
4. (in genetic studies) the degree of similarity in a pair of twins with respect to the presence or absence of a particular disease or trait.