1bi·en·ni·al 
/baɪˈɛnijəl/ adjective
always used before a noun /baɪˈɛnijəl/ adjective 1 : happening every two years
▪ The governor explained the biennial budget proposal. ▪ a biennial show 2 of a plant : living for only two years or seasons : having a life cycle that is two years or seasons long
▪ biennial plants/herbs/flowers — compare 1annual, 1perennial
▪ The governor explained the biennial budget proposal. ▪ a biennial show
▪ biennial plants/herbs/flowers — compare 1annual, 1perennial
— bi·en·ni·al·ly adverb
▪ The art show takes place biennially.
▪ The art show takes place biennially.
