What does "half-life" mean?
The time required for half the nuclei in a sample of an isotope to undergo radioactive decay.
Half-life
/ˈhæfˌlaɪf/ noun
noun ·Rare ·Advanced level
Meaning at a glance
- Primary sense: The time required for half the nuclei in a sample of an isotope to undergo radioactive decay.
- Grammar: half-life is listed as noun.
- Nearest alternatives: activity, decontamination, fallout, half life.
- Usage evidence: Plutonium-244 has a half-life of 80 million years.
How to use "half-life"
- Start with the primary definition, then check the part of speech before placing the word in a sentence.
- Compare nearby synonyms to make sure "half-life" carries the exact meaning, tone, and strength you need.
- Use the example sentence as a context check. If your sentence uses the word differently, confirm that the grammar still fits.
Meaning check
- Does the word fit the sentence's grammar?
- Does it match the intended tone rather than only the dictionary definition?
- Would a simpler synonym be clearer for the reader?
- Is there enough surrounding context to prevent ambiguity?
Source and review context
This entry combines structured lexical data with WordToolSet review checks. Definitions, examples, synonyms, and usage notes may come from different source tables, so the page is designed to show evidence from more than one angle before you rely on "half-life" in a final draft.
If a word has several senses, prefer the sense that matches your sentence's grammar and surrounding context. A correct definition can still be the wrong choice when the sentence needs a different register, emphasis, or level of specificity.
Before you rely on this definition
Read the first definition as a starting point, then check the example, synonyms, and part of speech before treating "half-life" as the right word for your sentence.
If your draft is formal, technical, persuasive, or sensitive, compare "half-life" with a nearby alternative so the final choice matches both meaning and reader expectation.
Compare nearby meanings
- Use synonyms when you need a softer, stronger, simpler, or more specific word.
- Use antonyms to check the boundary of the meaning and avoid accidental contrast.
- Use the example sentence to confirm the word behaves naturally in context.
- Keep the original wording when a replacement adds complexity without improving precision.
Definition decision workflow
1. Identify the role
Check whether "half-life" is acting as noun in your sentence. A definition is only useful when the grammar matches the way the word is being used.
2. Test the nearest option
Compare it with "activity" and other nearby choices to see whether the sentence needs a softer, stronger, or more familiar word.
3. Confirm with context
Use the example sentence below as an evidence check, then read your own sentence out loud to catch tone or rhythm problems.
Review note: Definition pages are checked for source coverage, sentence evidence, synonym support, and editorial insight before they are treated as approval-ready pages. If the evidence is too thin, the page remains available to users but is kept out of the approval-facing indexed inventory.
Final meaning check
Before publishing a sentence with "half-life", ask whether the word helps the reader understand the idea faster. A precise word should reduce confusion, not simply make the sentence look more polished.
When the definition, synonym evidence, and example context point in the same direction, the word is usually a safer choice. When they conflict, revise the sentence or choose a clearer alternative.
Definitions
Noun
- 1 The time required for half the nuclei in a sample of an isotope to undergo radioactive decay.
""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.""
- 2 the time required for something to fall to half its initial value (in particular, the time for half the atoms in a radioactive substance to disintegrate) wordnet
- 3 In a chemical reaction, the time required for the concentration of a reactant to fall from a chosen value to half that value. physical
- 4 The time it takes for a substance (drug, radioactive nuclide, or other) to lose half of its pharmacological, physiologic, or radiological activity.
"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."
- 5 The amount of time it takes for an idea or a fashion to lose half of its influential power.
"Most books of scholarship have surprisingly short intellectual half-lives during which they make a difference""
Synonyms
All synonymsExample
"Plutonium-244 has a half-life of 80 million years."
Common questions
What is a synonym for "half-life"?
Common synonyms include: activity, decontamination, fallout, half life, radiant energy, radioactivity.
How do you use "half-life" in a sentence?
Plutonium-244 has a half-life of 80 million years.
How do you pronounce "half-life"?
Pronounced /ˈhæfˌlaɪf/.
Etymology
From half- + life.