heptadn.
/ˈhɛptad/, U.S. /ˈhɛpˌtæd/ 1.
a. The sum or number of seven; a group of seven.
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. 63 The Heptad was so called, qu. σεπτὰς σεβασμοῦ ἄξιος, worthy of veneration.
1797 Monthly Mag. 3 521 The heptad of wandering animals.
1850 J. Brown Disc. & Sayings our Lord (1852) I. iv. 351 This prayer contains a sacred heptad of petitions.
b. spec. A group of seven days, a week; = hebdomad n.
ΘΚΠ
the world > time > period > a week > [noun]
weekeOE
sennightOE
seven daysOE
weekOE
seven days and seven nightsOE
(an) eight daysc1160
a week of daysa1382
week1398
sennight dayc1425
septimane1450
seventh night1567
sennight space1599
hebdomad1600
septuary1646
heptad1876
1876 J. Martin tr. C. F. Keil Biblical Comm. Ezekiel II. 336 A feast of heptads of days or weeks of days.
1881 J. S. Blackie Lay Serm. ii. 83 The months are divided into heptads.
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2. Chemistry. An atom or molecule whose equivalence is seven atoms of hydrogen, i.e. which can be combined with, substituted for, or replaced by seven atoms of hydrogen.
3. Music. A scheme of seven tones in the duodenal system of analysis, containing all the notes from which consonant triads may be formed with the tonic.
ΚΠ
1874 A. J. Ellis in Proc. Royal Soc. 23 11 The Harmonic Heptad or Unit of Chord-relationship..The heptad also contains all triads, consisting of three tones, two of which are consonant with C but dissonant with each other.
This entry has not yet been fully updated (first published 1898; most recently modified version published online March 2022).
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n.1660