hapt(o)-

Binding or fastening; touching.

Greek haptein, fasten.

A haptoglobin is a protein present in blood serum which binds to and removes free haemoglobin from the bloodstream; a hapten is a small molecule that can combine with a protein in the body to form an antigen which provokes the production of antibodies. The adjective haptic refers to the sense of touch, and haptics is the study of that sense and its applications.