decad

(This etymology is missing or incomplete. Please add to it, or discuss it at the Etymology scriptorium.) Doublet of decade. By surface analysis, dec- +‎ -ad.

• IPA^(key): /ˈdɛkæd/

decad (plural decads)

1. Archaic form of decade (“period of ten years”).
   • 1864, Alfred Tennyson, “Aylmer’s Field”, in Enoch Arden, &c., London: Edward Moxon & Co., […], →OCLC, page 55:

     Since Averill was a decad and a half / His elder, and their parents underground

2. Archaic form of decade (“group of ten”).
   • 1806, Aristotle, translated by Thomas Taylor, The Physics, or Physical Ausculation of Aristotle, page 167:

     Plato […] extends number as far as to the decad.

3. (music) A group of ten notes from which the consonant triads may be constructed

• (group) monad, duad/dyad, triad, tetrad, pentad, hexad, hebdomad/heptad, ogdoad/octad, ennead/nonad, decad/decade, hendecad, dodecad/duodecade, chiliad

• caded

• IPA^(key): [deˈkad]

decad

1. inflection of decădea:
   1. first-person singular present indicative/subjunctive
   2. third-person plural present indicative