bi·en·ni·al
adjective/baɪˈeniəl/
/baɪˈeniəl/
[usually before noun]- happening once every two years
两年一次的 - a biennial convention
两年召开一次的大会
Oxford Collocations DictionaryBiennial is used with these nouns:- meeting
Word Originearly 17th cent.: from Latin biennis (from bi- ‘twice’ + annus ‘year’) + -al. - a biennial convention