hapten

hap·ten

noun \ˈhap-ˌten\

Definition of HAPTEN

: a small separable part of an antigen that reacts specifically with an antibody but is incapable of stimulating antibody production except in combination with an associated protein molecule

—hap·ten·ic \hap-ˈten-ik\ adjective

—hap·ten·at·ed \ˈhap-tə-ˌnāt-əd\ adjective