As a noun decad
is .
As an adjective decadal is
of or pertaining to the number ten, a group of ten things, or to a decade.
decad
English
Noun
(
en noun)
* Averill was a decad and a half his elder. — Tennyson.
decadal
English
Adjective
(-)
Of or pertaining to the number ten, a group of ten things, or to a decade
