The region of the antibody molecule that enables each antibody to recognize a specific foreign structure (i.e., epitope or hapten) is said to have an idiotype (for that epitope or hapten). An identifying characteristic (or property) of the thing we are talking about.
The unique parts and characteristics of an antibody’s variable region. They may also serve as antigens.
In immunology, the set of antigenic determinants (idiotopes) on an antibody that make that antibody unique. It is determined by the amino acids of immunoglobulin light and heavy chains.