half-life
/ˈhæfˌlaɪf/
Word Rarity
Common
Frequency: 5.29 in modern English
17
Scrabble Score
8
Letters
2
Syllables
6
Unique Chars
Meaning
noun
In a chemical reaction, the time required for the concentration of a reactant to fall from a chosen value to half that value.
noun
The time it takes for a substance (drug, radioactive nuclide, or other) to lose half of its pharmacological, physiologic, or radiological activity.
Example Sentences
- ""The guy that just left—what's he got in his lungs?" / "Well, I'm not very sure. But the two best candidates are uranium-233 and plutonium-239, one or both." / "They're in his bones too, aren't they?" / "Yeah, they're both boneseekers. And they've got half-lives of one hundred sixty-two thousand and twenty-four thousand years respectively. So they stay hot for a long time.""
- "O₂^(•−) and OH^• are highly unstable (half-life at the level of microseconds and nanoseconds, respectively) and cannot cross membrane, while H₂O₂, though not a free radical but a ROS, is relatively stable (half-life around 1 ms) (Møller et al. 2007) and can cross membranes through aquaporins."
- "For nonporous surfaces such as steel, in a dark and low-humidity environment, the CCP virus has an 18-hour half-life—the time required for it to decrease by half , according to the researchers' findings."
- "Most books of scholarship have surprisingly short intellectual half-lives during which they make a difference""
Etymology
Etymology tree English half- Proto-Indo-European *leyp- Proto-Germanic *lībanąder. Proto-Germanic *lībą Proto-West Germanic *līb Old English līf Middle English lyf English life English half-life From half- + life.
Regional Pronunciation
- American English: /ˈhæfˌlaɪf/