hapten
noun
hap·ten ˈhap-ˌten 
: a small separable part of an antigen that reacts specifically with an antibody but is incapable of stimulating antibody production except in combination with a carrier protein molecule
haptenic
hap-ˈte-nik
adjective 
Word History
Etymology
borrowed from German Hapten, from Greek hapt- (stem of háptein "to fasten," háptesthai "to fasten oneself onto, grasp") + German -en (in Antigen antigen) — more at haptics
Note: Term introduced by Karl landsteiner in "Über heterogenetisches Hapten und Antigen," Biochemische Zeitschrift, Band 119 (1921), pp. 294-306.
First Known Use
1921, in the meaning defined above
Medical Definition
hapten
noun
hap·ten ˈhap-ˌten
: 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