half-life
/ˈhæfˌlaɪf/
"half-life" is a 8-letter English headword indexed on PlainSpell.
The verdict
“half-life” is uncommon English (outside the top frequency list), classed as a noun. The kind of spelling people second-guess.
- Unranked
- below top-frequency English
- 9
- letters
According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - The time required for half the nuclei in a sample of an isotope to undergo radioactive decay.
Corpus desk
Index EN-half-life · half-life · English
half-life · unranked · 0 variants · 0 confusables
- FREQ-UNRANKED Unranked
- LEN-LONG 9 letters
- VOW-3 3 vowels
- CONFUS-0 No pairs
- VAR-0 0 variants
- BOOK-THIN "H" thin
- PHOTO-UNK Peer pending
Read with this headword: Spelling guide for this pattern
Desk codes from Wiktionary headword shape, FrequencyWords rank tier, confusable-pair count, generated misspelling depth, letter-cohort book size, and photo-finish peer. Not a difficulty grade.
| Property | Value |
|---|---|
| Headword | half-life |
| Language | English |
| Part of speech | Noun |
| IPA | /ˈhæfˌlaɪf/ |
| Letters | 9 |
| Misspellings tracked | 0 |
| Confusable pairs | 0 |
| Source | Wiktionary (kaikki.org) |
Long-tail rank of “half-life” in English
Rare enough to double-check
half-life is uncommon English outside the top frequency list, classed as anoun, transcribed /ˈhæfˌlaɪf/. Rarity is why readers land here mid-draft. 4 senses are on record.
half-life doesn't appear in our generated misspelling index, suggesting the orthography follows predictable English patterns. Our dataset records no confusable match here, which tends to mean the word is visually distinctive enough to stand on its own.
Etymologically, the entry records: From half- + life. The correct English form is half-life, spelled H-A-L-F---L-I-F-E.
Definition
- 1The time required for half the nuclei in a sample of an isotope to undergo radioactive decay.
- 2In a chemical reaction, the time required for the concentration of a reactant to fall from a chosen value to half that value.
- 3The time it takes for a substance (drug, radioactive nuclide, or other) to lose half of its pharmacological, physiologic, or radiological activity.
- 4The amount of time it takes for an idea or a fashion to lose half of its influential power.
Recorded use
Wiktionary examplesThese source excerpts show how half-life appears in context. They illustrate usage; the definition above remains the entry’s reference meaning.
"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 ho…
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.
Etymology
From half- + life.
This word in other languages
Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA). See the methodology for how each field is sourced and updated.