half-life

• Tempo necessário para que uma quantidade se reduza à metade do seu valor inicial, especialmente o tempo em que metade dos átomos de uma substância radioativa se desintegra.

The time required for a quantity to reduce to half its initial value, especially the time taken for half the atoms in a radioactive substance to undergo decay.

1. Radioactive decayB2formalscientific

   The time required for half of the atoms in a radioactive substance to undergo decay.

   Meia-vida

   • 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. General declineC1formalscientific

   The time it takes for any quantity or substance to reduce to half its initial amount.

   Meia-vida

   • The half-life of a drug in the bloodstream determines dosage frequency.
   • Environmental pollutants have varying half-lives in soil.
   • The half-life of a chemical reaction depends on temperature.