Definition: A living organism on or in which a parasite, pathogen, commensal or symbiont lives (see Parasitism). Related Vocabulary: ParasiteParasitismPathogenSymbiontSymposia: Comparative Anthropogeny: From Molecules to SocietiesHumans: The Planet-Altering ApesImpact of Infectious Disease on Humans & Our OriginsMismatch: Human Origins and Modern Disease