half-life
/hæf laɪf/
NOUN
1. Radioactive decay period
The time required for half of the radioactive nuclei in a sample of a particular isotope to undergo radioactive decay.
1.1. Radioactivity and nuclear physics
Used in nuclear physics to describe the time needed for half of the unstable atomic nuclei in a radioactive substance to decay, indicating the rate at which the substance loses radioactivity.
Synonyms
- radioactive half-life
- half-time
- decay period
- half-period
Examples
- The concept of half-life is fundamental in understanding radioactive decay.
- Scientists study the half-life of various radioactive isotopes to determine their stability.
- Carbon-14 has a half-life of approximately 5,730 years, making it useful for dating ancient organic materials.
Related Words
- radioactive decay
- radioactivity
- isotope
- radionuclide
- nuclear radiation
- decay constant
- nuclear physics
NOUN
2. Time for a substance to lose half its concentration or activity
The period required for the concentration, amount, or biological, chemical, or pharmacological activity of a substance to decrease to half its initial value.
2.1. Chemical reactions and substance concentration
Used in chemistry to describe the time required for the concentration of a reactant to decrease to half its original value during a chemical reaction.
Synonyms
- half-time
- decay period
- half-period
Examples
- In chemistry, half-life calculations are essential for predicting the behavior of certain compounds in reactions.
- The reaction's half-life indicates how quickly the reactant concentration decreases over time.
- Researchers measured the half-life of the compound to understand its chemical stability.
Related Words
- reaction rate
- reactant
- concentration
- chemical kinetics
- decomposition
- decay constant
2.2. Medication and pharmacological activity
Used in pharmacology and medicine to describe the time required for the amount or concentration of a drug in the body, or its pharmacological activity, to decrease by half.
Synonyms
- elimination half-life
- biological half-life
- half-time
Examples
- The medication has a short half-life, requiring frequent dosing throughout the day.
- Doctors consider the drug's elimination half-life when determining an appropriate dosing schedule.
- A medication with a long biological half-life may remain active in the body for an extended period.
Related Words
- drug metabolism
- drug elimination
- plasma concentration
- pharmacokinetics
- dosage
- clearance
- absorption
NOUN
3. Decline in influence or popularity
The period required for an idea, fashion, trend, technology, or other phenomenon to lose half of its original influence, popularity, relevance, or perceived value.
3.1. Ideas, trends, and cultural influence
Used figuratively to describe how quickly an idea, fashion, cultural trend, or public interest loses half of its influence or popularity over time.
Synonyms
Examples
- The half-life of popular fashion trends seems to be getting shorter in the age of social media.
- The researcher examined the half-life of viral internet trends to understand how quickly public attention fades.
- In the technology industry, the half-life of certain innovations can be remarkably short.
Related Words
- popularity
- influence
- relevance
- cultural trend
- obsolescence
- public interest
- fashion cycle