half life

• Tiempo necesario para que una cantidad (por ejemplo, de una sustancia radiactiva, un fármaco en el organismo o una reacción química) se reduzca a la mitad de su valor inicial. También se usa metafóricamente para describir la velocidad de disminución o descomposición de algo a lo largo del tiempo.

The time required for a quantity (such as a radioactive substance, a drug in the body, or a chemical reaction) to reduce to half its initial value. Also used metaphorically to describe the rate of decline or decay of something over time.

1. Radioactive decayC1formal

   The time required for a quantity of a radioactive substance to reduce to half of its initial value.

   vida media

   • The half-life of carbon-14 is about 5,730 years.
   • Scientists use half-life to date ancient artifacts.
   • Uranium-238 has a half-life of 4.5 billion years.

2. Chemical eliminationC1formal

   The time it takes for the concentration of a substance (e.g., a drug) in the body to decrease by half.

   vida media

   • The drug has a half-life of approximately 12 hours.
   • Doctors consider the half-life when prescribing medication.
   • The half-life of caffeine in the human body is about 5 hours.