OCTAD

eight, VIII, eighter, eighter from Decatur, octad, ogdoad, octonary, octet

(noun) the cardinal number that is the sum of seven and one

Source: WordNet® 3.1

Etymology

Noun

octad (plural octads)

A group of eight things.

Synonym: octonary

(historical) hundred million = myriad myriad; 100,000,000 = 10⁸ [from 16th c.]

Coordinate terms

• monad · duad, dyad · triad · tetrad · pentad · hexad · heptad · octad · ennead, nonad · decad, decade · hendecad · dodecad, duodecade

Source: Wiktionary

Oc"tad, n. Etym: [Gr. (Chem.)

Definition: An atom or radical which has a valence of eight, or is octavalent.

Source: Webster’s Unabridged Dictionary 1913 Edition