median lethal concentration, \(\text{LC}_{50}\)

https://doi.org/10.1351/goldbook.M03809
Statistically derived concentration of a substance in an environmental medium expected to kill 50% of organisms in a given population under a defined set of conditions.
Source:
PAC, 1993, 65, 2003. (Glossary for chemists of terms used in toxicology (IUPAC Recommendations 1993)) on page 2068 [Terms] [Paper]