pentadn.

Brit.

/ˈpɛntad/, U.S.

/ˈpɛnˌtæd/

Origin: A borrowing from Greek. Etymons: Greek πεντάδ-, πεντάς.

Etymology: < ancient Greek πεντάδ-, πεντάς, later form of πεμπάδ- , πεμπάς the number five, a group of five < ancient Greek (Aeolic) πέμπε , variant of πέντε five (see penta- comb. form) + -άς -ad suffix¹. Compare German Pentade group of five things (1776 or earlier, referring to groups of five books in Livy's Ab urbe condita), period of five years (1893 or earlier; now rare). Compare post-classical Latin pentas the number five (4th cent.).In sense 3a after decade n.

1. Originally, in the Pythagorean system of numerology: the number five (now rare). Later: a group or set of five people or things.

ΘΚΠ

the world > relative properties > number > mathematical number or quantity > numerical arrangement > [noun] > set > elements in or parts of > specific number of

hebdomad1545

quaternion1549

tetractys1603

quaternary number1605

tetrad1653

heptad1660

pentad1660

quaternary of numbers1809

tripair1878

trey1887

1660 T. Stanley Hist. Philos. III. i. 61 The Pentad is the first complexion of both kinds of number, even and odd, two and three.

1662 H. More Conjectura Cabbalistica (new ed.) 125 in Coll. Several Philos. Writings (ed. 2) So manifest is it what special reason Pythagoras had to mention the Tetrad rather than the Pentad, or any other number, in that form of swearing by Him that first imparted the Cabbala.

1702 Lives Anc. Philosophers 349 The Pentad is the first complexion of even and odd.

1863 Proc. Royal Soc. 13 397 The chords may also be grouped according to the number of elements in their type, dyads containing two, triads three, tetrads four, and pentads five.

1887 E. C. Brewer Dict. Phr. & Fable (ed. 19) 466/1 Five, or the pentad, the great mystic number, being the sum of 2 + 3, the first even and first odd compound.

1891 S. R. Driver Introd. Lit. Old Test. (1892) 48 The laws appear often to be arranged in Pentads, or groups of five.

1973 L. L. Constantine & J. M. Constantine Group Marriage vi. 67 Two pentads (five partners) and two hexads (six partners) have been located.

1994 Prairie Fire Summer 13 The fighting fantasies never came in a single book, but in sets—trilogies and pentads.

2. Chemistry. A pentavalent element or group. Now rare.

ΘΚΠ

the world > matter > chemistry > valency > [noun] > combining powers of elements > element with the power of five

pentad1869

1869 Nature 9 Dec. 165/2 To term..potassium a pentad because we know of the body K₂S₅, appears to be an exaggeration of a useful doctrine.

1877 H. Watts Fownes's Man. Chem. I. 460 Vanadium was, till lately, regarded as a hexad metal..; but Roscoe has shown that it is a pentad.

1912 W. Tibbles Foods i. 18 When ammonia is approached by certain electro-negative groups or bodies, it loses its trivalent character and becomes a pentad.

1918 Philos. Trans. (Royal Soc.) A. 217 226 The replacement of two atoms of monad rubidium by eight atoms of monad hydrogen and two atoms of triad (at least, more probably pentad) nitrogen.

a. A period of five years. Cf. decade n. 2.

ΘΚΠ

the world > time > period > year > [noun] > period of specific number of years

hendecadOE

a week of yearsa1382

weekc1384

Olympiada1387

lustre1387

yearc1425

millenary1551

prenticeship1553

septenary1576

lustrum1590

quinquennal1590

seventy1590

septimane1603

quinquennie1606

threescore (years) and tena1616

duodecad1621

quinquennium1621

jubilee1643

quadrenniala1646

chiliad1653

septennary1659

septennium1660

triennial1661

millennium1664

tetraëterid1678

octennial1679

duodenary1681

quadrennium1779

septenniad1836

quinquenniad1842

milliad1843

tricentenary1846

triennium1847

vicennium1847

bimillenary1850

lustration1853

sexennium1858

septennate1874

quinquennial1877

pentad1880

sexennate1898

aeon1960

1880 J. D. Whitney Climatic Changes vii. 337 The means of the last two pentads, 1866–70 and 1871–75, were almost exactly the same as the grand mean.

1927 Geogr. Rev. 17 153 Quijano has listed the normal values of annual rainfall for 36 older stations alongside the means for this pentad.

1978 Nature 26 Jan. 322/2 South of lat 45° S, however, they conclude that average annual temperatures increased between the 1960–64 and 1970–74 pentads.

1991 Sunday Mail Mag. (Brisbane) 24 Feb. 18 (caption) ‘What do you call a series of five years?’ ‘A pentad.’

b. Chiefly Meteorology. A period of five days.

ΘΚΠ

the world > time > period > a day or twenty-four hours > [noun] > period of specific number of days

Lentc1450

quarantine1617

quarantain1638

soixantine1722

parson's week1790

nundine1860

trinundine1891

pentad1906

1906 W. Marriott Hints to Meteorol. Observers (ed. 6) 67/2 Pentad, a period of five days.

1935 Nature 12 Oct. 614/1 There has been great discussion of the relative advantages of the 5-day period, or pentad, and the week, with the result that both units have received international approval.

1959 R. E. Huschke Gloss. Meteorol. 416 Pentad, a group of five. In climatology, it is applied to a period of five consecutive days. It often is preferred to the week for climatological purposes since it is an exact factor of the 365-day year.

1990 Trans. Inst. Brit. Geographers 15 22/2 Rainfall probabilities by day, pentad and month for standard periods are available.

This entry has been updated (OED Third Edition, September 2005; most recently modified version published online March 2022).

单词	pentad
释义	pentadn. Brit. /ˈpɛntad/, U.S. /ˈpɛnˌtæd/ Origin: A borrowing from Greek. Etymons: Greek πεντάδ-, πεντάς. Etymology: < ancient Greek πεντάδ-, πεντάς, later form of πεμπάδ- , πεμπάς the number five, a group of five < ancient Greek (Aeolic) πέμπε , variant of πέντε five (see penta- comb. form) + -άς -ad suffix¹. Compare German Pentade group of five things (1776 or earlier, referring to groups of five books in Livy's Ab urbe condita), period of five years (1893 or earlier; now rare). Compare post-classical Latin pentas the number five (4th cent.).In sense 3a after decade n. 1. Originally, in the Pythagorean system of numerology: the number five (now rare). Later: a group or set of five people or things. ΘΚΠ the world > relative properties > number > mathematical number or quantity > numerical arrangement > [noun] > set > elements in or parts of > specific number of hebdomad1545 quaternion1549 tetractys1603 quaternary number1605 tetrad1653 heptad1660 pentad1660 quaternary of numbers1809 tripair1878 trey1887 1660 T. Stanley Hist. Philos. III. i. 61 The Pentad is the first complexion of both kinds of number, even and odd, two and three. 1662 H. More Conjectura Cabbalistica (new ed.) 125 in Coll. Several Philos. Writings (ed. 2) So manifest is it what special reason Pythagoras had to mention the Tetrad rather than the Pentad, or any other number, in that form of swearing by Him that first imparted the Cabbala. 1702 Lives Anc. Philosophers 349 The Pentad is the first complexion of even and odd. 1863 Proc. Royal Soc. 13 397 The chords may also be grouped according to the number of elements in their type, dyads containing two, triads three, tetrads four, and pentads five. 1887 E. C. Brewer Dict. Phr. & Fable (ed. 19) 466/1 Five, or the pentad, the great mystic number, being the sum of 2 + 3, the first even and first odd compound. 1891 S. R. Driver Introd. Lit. Old Test. (1892) 48 The laws appear often to be arranged in Pentads, or groups of five. 1973 L. L. Constantine & J. M. Constantine Group Marriage vi. 67 Two pentads (five partners) and two hexads (six partners) have been located. 1994 Prairie Fire Summer 13 The fighting fantasies never came in a single book, but in sets—trilogies and pentads. 2. Chemistry. A pentavalent element or group. Now rare. ΘΚΠ the world > matter > chemistry > valency > [noun] > combining powers of elements > element with the power of five pentad1869 1869 Nature 9 Dec. 165/2 To term..potassium a pentad because we know of the body K₂S₅, appears to be an exaggeration of a useful doctrine. 1877 H. Watts Fownes's Man. Chem. I. 460 Vanadium was, till lately, regarded as a hexad metal..; but Roscoe has shown that it is a pentad. 1912 W. Tibbles Foods i. 18 When ammonia is approached by certain electro-negative groups or bodies, it loses its trivalent character and becomes a pentad. 1918 Philos. Trans. (Royal Soc.) A. 217 226 The replacement of two atoms of monad rubidium by eight atoms of monad hydrogen and two atoms of triad (at least, more probably pentad) nitrogen. 3. a. A period of five years. Cf. decade n. 2. ΘΚΠ the world > time > period > year > [noun] > period of specific number of years hendecadOE a week of yearsa1382 weekc1384 Olympiada1387 lustre1387 yearc1425 millenary1551 prenticeship1553 septenary1576 lustrum1590 quinquennal1590 seventy1590 septimane1603 quinquennie1606 threescore (years) and tena1616 duodecad1621 quinquennium1621 jubilee1643 quadrenniala1646 chiliad1653 septennary1659 septennium1660 triennial1661 millennium1664 tetraëterid1678 octennial1679 duodenary1681 quadrennium1779 septenniad1836 quinquenniad1842 milliad1843 tricentenary1846 triennium1847 vicennium1847 bimillenary1850 lustration1853 sexennium1858 septennate1874 quinquennial1877 pentad1880 sexennate1898 aeon1960 1880 J. D. Whitney Climatic Changes vii. 337 The means of the last two pentads, 1866–70 and 1871–75, were almost exactly the same as the grand mean. 1927 Geogr. Rev. 17 153 Quijano has listed the normal values of annual rainfall for 36 older stations alongside the means for this pentad. 1978 Nature 26 Jan. 322/2 South of lat 45° S, however, they conclude that average annual temperatures increased between the 1960–64 and 1970–74 pentads. 1991 Sunday Mail Mag. (Brisbane) 24 Feb. 18 (caption) ‘What do you call a series of five years?’ ‘A pentad.’ b. Chiefly Meteorology. A period of five days. ΘΚΠ the world > time > period > a day or twenty-four hours > [noun] > period of specific number of days Lentc1450 quarantine1617 quarantain1638 soixantine1722 parson's week1790 nundine1860 trinundine1891 pentad1906 1906 W. Marriott Hints to Meteorol. Observers (ed. 6) 67/2 Pentad, a period of five days. 1935 Nature 12 Oct. 614/1 There has been great discussion of the relative advantages of the 5-day period, or pentad, and the week, with the result that both units have received international approval. 1959 R. E. Huschke Gloss. Meteorol. 416 Pentad, a group of five. In climatology, it is applied to a period of five consecutive days. It often is preferred to the week for climatological purposes since it is an exact factor of the 365-day year. 1990 Trans. Inst. Brit. Geographers 15 22/2 Rainfall probabilities by day, pentad and month for standard periods are available. This entry has been updated (OED Third Edition, September 2005; most recently modified version published online March 2022). < n.1660
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