the specific part of an antigen (binding partner) that an antibody binds to (“recognizes”). Normally we talk more generally about antibodies “recognizing” (binding to) antigens (e.g. an anti-GFP antibody would bind to the protein GFP), but the precise spot the antibody binds to is called the epitope. Antigens can have multiple epitopes, each of which may be recognized by a different antibody. There is nothing “inherent” to the antigen about an epitope, the word only really has meaning in relationship to a corresponding antibody.