tetradn.

/ˈtɛtrəd/

Etymology: < Greek τετράς (τετραδ-) a group of four, the number four.

1. A sum, group, or set of four; four (things, etc.) regarded as a single object of thought.

ΘΚΠ

the world > relative properties > number > specific numbers > four > [noun] > group of four

quaternionc1384

quadrivial?a1475

messa1529

quaternity1529

quaternio1601

mournival1631

quadrate1637

quaternarya1638

tetrad1653

quadruplet1795

quartetto1807

quatrain1862

quartet1882

quad1896

society > faith > artefacts > symbol (general) > Christian symbols or images > [noun] > representing God

tetractys1603

tetrad1653

the mind > mental capacity > philosophy > ancient Greek philosophy > pre-Socratic schools of philosophy > [noun] > Pythagorean philosophy > elements of

tetractys1603

tetrad1653

tetractysm1846

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

1653 H. More Second Lash of Alazonomastix (1713) 82 It was a solemn Oath..to swear by him that delivered to them the mystery of the Tetractys, Tetrad, or number Four.

1653 H. More Second Lash of Alazonomastix (1713) 4 The Pythagoreans Oath, swearing by him that taught them the mystery of the Tetractys, or the number Four.

1832 S. T. Coleridge Table-talk 24 Apr. The adorable tetractys, or tetrad, is the formula of God.

1895 Athenæum 2 Feb. 151/1 The great tetrad of senior wranglers of 1840 to 1843.

2. In spec. uses.

a. Chemistry. An element, compound, or radical having a combining power of four units, i.e. of four atoms of hydrogen; a tetravalent element, etc.

ΘΚΠ

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

tetrad1865

1865 Reader 1 Apr. 372/3 A tetratomic atom or tetrad.

1866 H. E. Roscoe Lessons Elem. Chem. xxvii. 242 As in mineral chemistry we have radicals.., some of which are monads, and some dyads, triads, or tetrads.

1868 H. B. Jones & H. Watts Fownes's Man. Elem. Chem. (ed. 10) 259 Silicium and titanium are tetrads.

b. Biology (a) A group of four cells, e.g. spores, pollen-grains. (b) A group of four chromosomes formed by the division of a single chromosome. (c) A quaternary unit of organization differentiated from a triad.

ΘΚΠ

the world > life > biology > substance > cell > [noun] > mass or group of

polyblast1873

tetrad1876

triad1876

tetrad-deme1883

stem-line1892

paraganglion1907

polyclone1975

the world > life > biology > biological processes > genetic activity > genetic components > [noun] > chromosome > group of chromosomes

tetrad1876

ring chromosome1895

genome1926

ring1949

1876 tr. P. Schützenberger On Fermentation 52 In the tetrads arranged in the form of a cross, we observe, also, two plane surfaces at right angles.

1882 S. H. Vines tr. J. von Sachs Text-bk. Bot. (ed. 2) 456 The cavity of the sporangium becomes filled with a granular plasma in which lie the mother-cells and the tetrads of spores... All the spores of the sixteen tetrads formed in the microsporangia reach maturity.

1883 [see tetrad-deme n. at Compounds 2].

1895 F. W. Oliver et al. tr. A. Kerner von Marilaun Nat. Hist. Plants II. 101 In Rhododendron hirsutum all the pollen-tetrads of an anther-cavity are held together by a mass of sticky viscin.

a1909 Wilson (cited in C.D. Suppl. in sense b)

1909 J. W. Jenkinson Exper. Embryol. 108 Granules of chromatin took the place of the tetrads and were unequally distributed to the spindle poles.

c. Music. A chord of four notes (after triad n.).

ΘΚΠ

society > leisure > the arts > music > musical sound > harmony or sounds in combination > chord > [noun] > other chords

seventh1591

fourth1597

sixth1597

fifth1631

tierce1696

septime1725

repercussion1728

octave1749

substitution1784

triad1786

German sixth1812

French sixth1813

nintha1830

Neapolitan sixth1871

six-four1873

Italian sixth1875

tetrad1881

added sixth1888

leading seventh1889

ninth chord1889

under-chord1890

diminished seventh1926

1881 J. Broadhouse Student's Helmholtz 332 The great majority of major tetrads in Palestrina's Stabat Mater are in the positions 1, 10, 8, 5, 3, 2, 4, 9.

d. In ancient systems of arithmetical notation: A group or series of four characters corresponding to successive powers of ten.

ΘΚΠ

the world > relative properties > number > mathematical notation or symbol > [noun] > scale > types of

algorism?c1225

binary scale1796

scale of (two, etc.)1871

tetrad1883

1883 E. C. Bayley Geneal. Mod. Numerals ii. 90 They [the Greeks] had however a system of ‘octads’ and ‘tetrads’ for expressing numbers of very high value.

e. Mathematics. (See quot. 1889.)

ΘΚΠ

the world > relative properties > number > geometry > point > [noun] > sets or groups of points

umbilic point1586

involution1847

triad1850

range1859

point group1887

tetrad1889

tristigm1889

neighbourhood1891

trinode1891

trigraphy1895

Cantor set1902

web1909

limit cycle1918

Leech lattice1968

1889 A. Cayley Coll. Math. Papers XII. 590 The term ‘tetrad’ is used in two distinct..senses, viz. a tetrad denotes any four points; and it also denotes the four vertices of a self-conjugate tetrahedron in regard to a quadric surface... Two or more tetrads, in regard to one and the same quadric surface, are called similar tetrads.

f. Ecology. (See quot. 1976.)

ΘΚΠ

the world > life > biology > balance of nature > environment or habitat > [noun] > portion of

subregion1830

province1847

realm1854

substrate1876

quadrat1904

transect1905

biotope1909

basal cover1923

microhabitat1931

basal area1938

tetrad1963

1963 Hawkes & Readett in P. J. Wanstall Local Floras 37 We soon realized that it would be impossible to record from every basic square in the county and we modified the method by considering the squares in blocks of four (‘tetrads’) and selecting one square at random from each tetrad for surveying.

1968 Watsonia VI. 351 This involved the detailed survey of 1 km squares as the unit of recording, one square at random being selected from each block of four or ‘tetrad’.

1976 J. G. Dony Bedfordshire Plant Atlas 10/1 It has become usual in the survey of areas as small as Bedfordshire to divide the ten-kilometre grid squares into 25 smaller squares each 2 km. × 2 km. known as tetrads. Each tetrad has an area of four square kilometres.

1983 Nat. World Spring 18 Distributional maps based on 2 × 2 kilometre squares, or tetrads.

Compounds

C1. attributive, as tetrad metal, tetrad term.

ΚΠ

1866 W. Odling Lect. Animal Chem. 17 The fourth or tetrad term of our series of typical hydrides.

1868 H. B. Jones & H. Watts Fownes's Man. Elem. Chem. (ed. 10) 445 Tin is a tetrad metal.

C2.

tetrad-deme n. Biology an aggregation of tetrads: see 2b (b) and deme n.² 2.

ΘΚΠ

the world > life > biology > substance > cell > [noun] > mass or group of

polyblast1873

tetrad1876

triad1876

tetrad-deme1883

stem-line1892

paraganglion1907

polyclone1975

1883 P. Geddes in Encycl. Brit. XVI. 843/2 Starting from the unit of the first order, the plastid or monad, and terming any undifferentiated aggregate a deme, we have a monad-deme integrating into a secondary unit or dyad, this rising through dyad-demes into a triad, this forming triad-demes, and these when differentiated becoming tetrads, the Botryllus-colony with which the evolution of compound individuality terminates being a tetrad-deme.

This entry has not yet been fully updated (first published 1911; most recently modified version published online September 2020).

单词	tetrad
释义	tetradn. /ˈtɛtrəd/ Etymology: < Greek τετράς (τετραδ-) a group of four, the number four. 1. A sum, group, or set of four; four (things, etc.) regarded as a single object of thought. ΘΚΠ the world > relative properties > number > specific numbers > four > [noun] > group of four quaternionc1384 quadrivial?a1475 messa1529 quaternity1529 quaternio1601 mournival1631 quadrate1637 quaternarya1638 tetrad1653 quadruplet1795 quartetto1807 quatrain1862 quartet1882 quad1896 society > faith > artefacts > symbol (general) > Christian symbols or images > [noun] > representing God tetractys1603 tetrad1653 the mind > mental capacity > philosophy > ancient Greek philosophy > pre-Socratic schools of philosophy > [noun] > Pythagorean philosophy > elements of tetractys1603 tetrad1653 tetractysm1846 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 1653 H. More Second Lash of Alazonomastix (1713) 82 It was a solemn Oath..to swear by him that delivered to them the mystery of the Tetractys, Tetrad, or number Four. 1653 H. More Second Lash of Alazonomastix (1713) 4 The Pythagoreans Oath, swearing by him that taught them the mystery of the Tetractys, or the number Four. 1832 S. T. Coleridge Table-talk 24 Apr. The adorable tetractys, or tetrad, is the formula of God. 1895 Athenæum 2 Feb. 151/1 The great tetrad of senior wranglers of 1840 to 1843. 2. In spec. uses. a. Chemistry. An element, compound, or radical having a combining power of four units, i.e. of four atoms of hydrogen; a tetravalent element, etc. ΘΚΠ the world > matter > chemistry > valency > [noun] > combining powers of elements > element with the power of four tetrad1865 1865 Reader 1 Apr. 372/3 A tetratomic atom or tetrad. 1866 H. E. Roscoe Lessons Elem. Chem. xxvii. 242 As in mineral chemistry we have radicals.., some of which are monads, and some dyads, triads, or tetrads. 1868 H. B. Jones & H. Watts Fownes's Man. Elem. Chem. (ed. 10) 259 Silicium and titanium are tetrads. b. Biology (a) A group of four cells, e.g. spores, pollen-grains. (b) A group of four chromosomes formed by the division of a single chromosome. (c) A quaternary unit of organization differentiated from a triad. ΘΚΠ the world > life > biology > substance > cell > [noun] > mass or group of polyblast1873 tetrad1876 triad1876 tetrad-deme1883 stem-line1892 paraganglion1907 polyclone1975 the world > life > biology > biological processes > genetic activity > genetic components > [noun] > chromosome > group of chromosomes tetrad1876 ring chromosome1895 genome1926 ring1949 1876 tr. P. Schützenberger On Fermentation 52 In the tetrads arranged in the form of a cross, we observe, also, two plane surfaces at right angles. 1882 S. H. Vines tr. J. von Sachs Text-bk. Bot. (ed. 2) 456 The cavity of the sporangium becomes filled with a granular plasma in which lie the mother-cells and the tetrads of spores... All the spores of the sixteen tetrads formed in the microsporangia reach maturity. 1883 [see tetrad-deme n. at Compounds 2]. 1895 F. W. Oliver et al. tr. A. Kerner von Marilaun Nat. Hist. Plants II. 101 In Rhododendron hirsutum all the pollen-tetrads of an anther-cavity are held together by a mass of sticky viscin. a1909 Wilson (cited in C.D. Suppl. in sense b) 1909 J. W. Jenkinson Exper. Embryol. 108 Granules of chromatin took the place of the tetrads and were unequally distributed to the spindle poles. c. Music. A chord of four notes (after triad n.). ΘΚΠ society > leisure > the arts > music > musical sound > harmony or sounds in combination > chord > [noun] > other chords seventh1591 fourth1597 sixth1597 fifth1631 tierce1696 septime1725 repercussion1728 octave1749 substitution1784 triad1786 German sixth1812 French sixth1813 nintha1830 Neapolitan sixth1871 six-four1873 Italian sixth1875 tetrad1881 added sixth1888 leading seventh1889 ninth chord1889 under-chord1890 diminished seventh1926 1881 J. Broadhouse Student's Helmholtz 332 The great majority of major tetrads in Palestrina's Stabat Mater are in the positions 1, 10, 8, 5, 3, 2, 4, 9. d. In ancient systems of arithmetical notation: A group or series of four characters corresponding to successive powers of ten. ΘΚΠ the world > relative properties > number > mathematical notation or symbol > [noun] > scale > types of algorism?c1225 binary scale1796 scale of (two, etc.)1871 tetrad1883 1883 E. C. Bayley Geneal. Mod. Numerals ii. 90 They [the Greeks] had however a system of ‘octads’ and ‘tetrads’ for expressing numbers of very high value. e. Mathematics. (See quot. 1889.) ΘΚΠ the world > relative properties > number > geometry > point > [noun] > sets or groups of points umbilic point1586 involution1847 triad1850 range1859 point group1887 tetrad1889 tristigm1889 neighbourhood1891 trinode1891 trigraphy1895 Cantor set1902 web1909 limit cycle1918 Leech lattice1968 1889 A. Cayley Coll. Math. Papers XII. 590 The term ‘tetrad’ is used in two distinct..senses, viz. a tetrad denotes any four points; and it also denotes the four vertices of a self-conjugate tetrahedron in regard to a quadric surface... Two or more tetrads, in regard to one and the same quadric surface, are called similar tetrads. f. Ecology. (See quot. 1976.) ΘΚΠ the world > life > biology > balance of nature > environment or habitat > [noun] > portion of subregion1830 province1847 realm1854 substrate1876 quadrat1904 transect1905 biotope1909 basal cover1923 microhabitat1931 basal area1938 tetrad1963 1963 Hawkes & Readett in P. J. Wanstall Local Floras 37 We soon realized that it would be impossible to record from every basic square in the county and we modified the method by considering the squares in blocks of four (‘tetrads’) and selecting one square at random from each tetrad for surveying. 1968 Watsonia VI. 351 This involved the detailed survey of 1 km squares as the unit of recording, one square at random being selected from each block of four or ‘tetrad’. 1976 J. G. Dony Bedfordshire Plant Atlas 10/1 It has become usual in the survey of areas as small as Bedfordshire to divide the ten-kilometre grid squares into 25 smaller squares each 2 km. × 2 km. known as tetrads. Each tetrad has an area of four square kilometres. 1983 Nat. World Spring 18 Distributional maps based on 2 × 2 kilometre squares, or tetrads. Compounds C1. attributive, as tetrad metal, tetrad term. ΚΠ 1866 W. Odling Lect. Animal Chem. 17 The fourth or tetrad term of our series of typical hydrides. 1868 H. B. Jones & H. Watts Fownes's Man. Elem. Chem. (ed. 10) 445 Tin is a tetrad metal. C2. tetrad-deme n. Biology an aggregation of tetrads: see 2b (b) and deme n.² 2. ΘΚΠ the world > life > biology > substance > cell > [noun] > mass or group of polyblast1873 tetrad1876 triad1876 tetrad-deme1883 stem-line1892 paraganglion1907 polyclone1975 1883 P. Geddes in Encycl. Brit. XVI. 843/2 Starting from the unit of the first order, the plastid or monad, and terming any undifferentiated aggregate a deme, we have a monad-deme integrating into a secondary unit or dyad, this rising through dyad-demes into a triad, this forming triad-demes, and these when differentiated becoming tetrads, the Botryllus-colony with which the evolution of compound individuality terminates being a tetrad-deme. This entry has not yet been fully updated (first published 1911; most recently modified version published online September 2020). < n.1653
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