half-lifen.adj.
/ˈhɑːflʌɪf/, U.S. /ˈhæfˌlaɪf/ (as adjective)Brit. /ˌhɑːfˈlʌɪf/, U.S. /ˌhæfˈlaɪf/ A. n.
1. The condition of being only partly or not fully alive; a reduced, limited, or unsatisfactory way of life. Also: a life of half the full or normal length.
ΘΚΠ
the world > life > source or principle of life > [noun] > manner of life > specific
over-living1817
work life1850
pseudo-life1853
half-life1864
vie d'intérieur1889
anti-life1926
1561 T. Norton tr. J. Calvin Inst. Christian Relig. ii. f. 35v For where is that half life [L. relictus esse semiuiuus], vnlesse some portion both of right reason and will remayned?
1639 W. Cartwright Royall Slave ii. vi. sig. D3 To crush those Reliques of an halfe-life, that Her doubtfull body faintly breaths.
1649 R. Baxter Saints Everlasting Rest (1650) i. vii. 89 The comforts that flow through Sermons..are but half comforts; and the Life that comes by these, is but a half life.
1740 J. Lockman Some Reflexions conc. Operas p. xvii in Rosalinda The first kind of Music, (to which Longinus gives the Name of Sounds, that enjoy only a Half-life) tho' ever so pleasing, will cloy by frequent Repetition.
1761 tr. C. Batteux Course Belles Lettres I. 183 Music has a meaning even in the symphony, which is but a kind of half-life, or lesser part of its existence.
1873 W. Mathews Getting on in World xx. 341 Is there not, as one has said, a vast difference between a half-life and half a life.
1963 Times Lit. Suppl. 31 May 393/4 The half-life which men were leading.
2006 Sydney Morning Herald (Nexis) 25 Nov. (Spectrum section) 33 Their schizophrenic mother endures a kind of half-life upstairs in the care of her sister.
2.
a. Physics. The time taken for the radioactivity of a specified isotope to fall to half its original value, i.e. the time in which half of the atoms in any sample of the isotope will undergo decay. Also: the time required for half of any number of unstable subatomic particles (esp. neutrons) to decay.Recorded earliest in half-life period n. at Compounds.
ΘΠ
the world > matter > physics > atomic nucleus > radioactive isotope > radioactive nuclide > [noun] > average duration > time of decrease
1907 Jrnl. Chem. Soc. 91 ii. 1281 Rutherford and others have shown that whilst radium A, B, and C have a life-period of only a few hours, radium D has a half-life-period of forty years.
1911 Times 31 Aug. 8/4 Radium C1 has a half-life of 19·5 minutes.
1954 H. Semat Introd. Atomic & Nucl. Physics (ed. 3) xi. 363 The value of the half-life of the neutron was calculated from a determination of the density of the neutron beam and the number of neutrons decaying per unit time per unit volume.
1972 Nature 22 Dec. 465/1 Because 244Pu has an 82 m.y. half life, its presence today, 56 half lives after the formation of the Earth, is a most impressive accomplishment.
2011 M. Irvine Nucl. Power: Very Short Introd. vii. 94 Tritium has a half-life of about 12 years and so does not accumulate on geological timescales rendering its natural abundance essentially zero.
b. The time in which the amount of a specified substance or the number of specified objects in a sample decreases by half; the mean expected lifetime of a given entity in a population (cf. lifetime n. 2b).
ΘΚΠ
the world > life > biology > laboratory analysis > material > [noun] > sample > half-life of
half-time1940
half-life1942
1942 Jrnl. Biol. Chem. 144 553 It was found that the half life of an antibody molecule is about 2 weeks.
1953 Proc. Iowa Acad. Sci. 60 659 The half-life of the original nests, with a desertion rate of 0.1464, is 4.7 years calculated by the second method.
1973 Jrnl. N.Y. Entomol. Soc. 71 221 King and Sallee..have calculated the half-life, that point in time on a modified survivorship curve at which the mixed-age population of a particular year has declined by one-half.
2011 Urban Forestry & Urban Greening 10 269 Based on the meta-analysis, we estimated that street tree annual survival rates ranged from 94.9 to 96.5%, and street tree population half-life ranged from 13 to 20 years.
c. Chiefly Pharmacology. The time required for the elimination, inactivation, or breakdown of half of the amount of a drug or other exogenous substance administered to a living organism.
Π
1947 Trans. N.Y. Acad. Sci. 9 254 Figure 4 shows the calculated half-life for the tagged TMV [= tobacco mosaic virus] in the mouse.
1996 Pulse 20 Apr. 47 (advt.) Gopten is the ACE inhibitor with the longest half life.
2015 Sci. Amer. Apr. 32/1 The first approved nanotherapy for cancer..has a half-life in the bloodstream that allows it to survive much longer than its conventional chemotherapy cousin, doxorubicin.
d. In figurative contexts, with reference to anything that is expected to decline or fade away over time, esp. with the implication that the period during which it flourishes or is effective will be brief.
Π
1963 Time 3 May 88/2 New engineering graduates can expect a professional ‘half-life’ of only ten years. Half of what they now know will be obsolete in 1973, and only half of what they will need to know is available to them at this time.
1978 Time 11 Dec. 90 In the mercurial cosmetics business, almost all products have short half-lives.
1989 N.Y. Times Bk. Rev. 29 Oct. 26/1 Many of the recent ‘revolutions’ in science and technology seem to have the half-life of an average teen-age crush.
2015 Sunday Times (Nexis) 1 Mar. (Culture section) 40 Sadly, this talented writer is proving to have a very short half-life.
B. adj.
Of a portrait or statue: of half the size as the original in life. Also: designating this size or scale of representation.
ΘΠ
society > leisure > the arts > visual arts > painting and drawing > painting > painting according to subject > [adjective] > portrait-painting > full-length, half-length, etc.
three-quarter1713
half-lengtha1739
Kit-cat1754
head-and-shoulders1822
1722 J. Richardson Acct. Statues Italy 31 Madonna Lattante, half Life.
1832 Spectator 8 Sept. 852/1 The half-life size..is ‘the happy medium’ between life size and miniature.
1867 D. G. Rossetti Let. 25 July (1965) II. 624 He would prefer a half-life scale.
1913 Bull. Metrop. Mus. Art 8 135 Six heads, fragments from wall-statues of Buddha, ranging in size from about half life to miniature size.
2013 P. Major Thomas Killigrew & 17th-cent. Eng. Stage Introd. 6 The half-life portrait by Van Dyck.
Compounds
half-life period n. the time taken for the quantity or value of something (esp. radioactivity) to fall to half its original value; cf. sense A. 2.
Π
1907 Jrnl. Chem. Soc. 91 ii. 1281 Rutherford and others have shown that whilst radium A, B, and C have a life-period of only a few hours, radium D has a half-life-period of forty years.
1942 J. D. Stranathan ‘Particles’ of Mod. Physics viii. 326 The half life period T of a radioactive substance is defined as the time required for one half of the active material present at any time to decay.
2008 Wear 265 627/1 The active species must have a half-life period compatible with the duration of the measurement.
This entry has been updated (OED Third Edition, December 2022).
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n.adj.1561