the variation, induced by a substance foreign to the body, in cellular or biochemical components or processes, structures, or functions that is measurable in a biological system or sample (McCarthy et al 1991: 2)
Any parameter that can be used to measure an interaction between a biological system and an environment agent, which may be chemical, physical or biological (WHO 1993)
a physical, functional, or biochemical indicator (e g , the presence of a particular metabolite) of a physiological or disease process
A molecular indicator of a specific biological property; a biochemical feature or facet that can be used to measure the progress of disease or the effects of treatment
Biochemical, physiological, or histological indicators of either exposure to or effects of xenobiotic chemicals at the suborganismal or organismal level (Huggett et al 1992)