heptad

American  

[hep-tad] / ˈhɛp tæd /

noun

1. the number seven.

2. a group of seven.

3. Chemistry.  an element, atom, or group having a valence of seven.

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heptad British  

/ ˈhɛptæd /

noun

1. a group or series of seven

2. the number or sum of seven

3. an atom or element with a valency of seven

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Etymology

Origin of heptad

First recorded in 1650–60, heptad is from the Greek word heptad- (stem of heptás ). See hepta-, -ad ¹

Example Sentences

Seven, or the heptad, is a number very powerful for good or for evil.

From Project Gutenberg

Thus one of the Meta molecules of iron, containing seven atoms, is identical in appearance with a Hyper heptad, but the latter dissociates into seven atoms, the former into two triads and a single atom.

From Project Gutenberg

Indeed, the heptad of things finite is in all cases reducible to the pentad.

From Project Gutenberg

The word pentad at once recalls to you the way in which the chemist speaks of a monad, triad, heptad, when he deals with elements.

From Project Gutenberg

Colours may best be expressed by a heptad, the largest possible formula for things finite, as the pentad is the smallest possible form.

From Project Gutenberg