Triannual vs. Triennial

Triannualadjective

Happening three times each year.

Triennialadjective

Happening every three years.

Triennialadjective

Lasting for three years.

Triennialnoun

A third anniversary.

Triennialnoun

A plant that requires three years to complete its life-cycle.

Triennialadjective

Continuing three years; as, triennial parliaments; a triennial reign.

Triennialadjective

Happening, coming about, or appearing once in every three years; as, triennial elections; a triennial catalogue; a triennial visitation.

Triennialnoun

Something which takes place or appears once in three years.

Triennialnoun

the 300th anniversary (or the celebration of it)

Triennialadjective

occurring every third year or lasting 3 years