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be biennial
biennial 作形容词表示生长周期为两年时，常作表语，放在 be 动词之后。
These plants are biennial, so they bloom in their second year.
这些植物是两年生的，所以它们第二年开花。
两年一次的
先理解核心含义，再看它在真实句子里的用法。
两年一次的
Happening once every two years.
These plants are biennial, so they bloom in their second year.
这些植物是两年生的，所以它们第二年开花。
每两年发生一次的。
Happening every two years.
持续两年的。
Lasting for two years.
Carrots and parsley are biennials that flower in their second year.
胡萝卜和欧芹是两年生植物，在第二年开花。
The garden's biennial plants were sown last year and will flower this spring.
园里的两年生植物是去年播种的，今年春天会开花。
The city hosts a biennial music festival that draws international artists.
这座城市每两年举办一次音乐节，吸引国际艺术家。
biennial 作形容词表示生长周期为两年时，常作表语，放在 be 动词之后。
These plants are biennial, so they bloom in their second year.
这些植物是两年生的，所以它们第二年开花。
biennial 作形容词表示“每两年一次的”时，放在名词前作定语。
The biennial festival is held in June.
这个两年一度的节日在六月举行。
biennial 作名词指两年生植物，也可指两年举办一次的活动；复数形式为 biennials。
A biennial takes two years to complete its life cycle.
两年生植物需要两年时间完成生命周期。
Not this
We have a biennial meeting in January and another in July.
Use this
We have a biannual meeting in January and another in July.
biennial 意为“两年一次的”，而 biannual 意为“一年两次的”。句中 January 和 July 指同一年内的两次会议，应使用 biannual。这两个词容易混淆。
Not this
The exhibition takes place biennial.
Use this
The exhibition takes place biennially.
biennial 是形容词/名词，不是副词。修饰动词短语 takes place 需用副词形式 biennially（每两年一次地）。英语中形容词不能直接作状语，这与汉语不同。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
两年生植物
The foxglove is a biennial plant that blooms in its second year.
毛地黄是两年生植物，在第二年开花。
两年一届的活动
The art exhibition is a biennial event that attracts visitors from around the world.
这个艺术展是两年一届的活动，吸引着来自世界各地的游客。
两年一次的选举
The club holds biennial elections for its officers.
该俱乐部每两年举行一次官员选举。
两年一次的会议
She presented her research at the biennial conference.
她在两年一次的会议上展示了她的研究。
两年一次的报告
The committee publishes a biennial report on its activities.
委员会每两年发布一份关于其活动的报告。
种植两年生植物
Many gardeners grow biennials from seed in early summer.
许多园丁在初夏用种子种植两年生植物。
Use biennial naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
联想记忆：bi（二）+ annual（年）→ biennial（两年一次）。
语域：formal 常见场景：botany、official documents、event scheduling biennial 多用于正式或专业语境，如植物学、官方文书和定期活动安排；日常口语中更常说 every two years。
biennials
Dictionary facts from ECDICT, WIKTIONARY.