Decad is a see also of polyad.
As nouns the difference between decad and polyad
is that decad is while polyad is a group consisting of an indeterminate number of things or people.
decad
English
Noun
(
en noun)
* Averill was a decad and a half his elder. — Tennyson.
polyad
English
See also
* monad
* dyad
* triad
* tetrad
* pentad
* hexad
* heptad
* octad
* nonad
* decad
* See also