MEANING: adjective: Yearly.

ETYMOLOGY: From Latin quot (how many) + annus (year). Earliest documented use: 1878. A related word is quotidian (happening every day; commonplace).

USAGE: “The Dallas Cowboys defense has been a point of contention with fans over the past few years.”
Daniel Ruppert; Dallas Cowboys: Quality vs Quantity, the Quotennial Question; FanSided; Feb 14, 2017.

DUOTENNIAL - twentyful

QUOTERNIAL - attributed to William R. Hamilton the system of imaginary numbers i, j, k with the properties ij=k, jk=i, ki=j, and i^2 = j^2 = k^2 = -1

QUITENNIAL - my yearly attempt to stop