Glossary of "Biology (3rd ed.)" by Hardin & Bajema (1978)
- the time taken for an organ to eliminate, through biological processes, one-half of the quantity of a substance that has been introduced into it.
- Hardin, G. & Bajema, C. 1978. Biology, its Principles and Implications, third edition. -x + 790 pp. W. H. Freeman and Company, San Francisco.