English Reference
adjective · noun

biennial

adj. · n.
US /baɪˈɛniəɫ/ UK /baɪˈɛnɪəl/ bi·en·ni·al UK spelling biennials

  1. 01 C1 Advanced Formal

    adj.happening once every two years.

    adj.occurring or taking place every other year; not to be confused with biannual.

    Simple

    The city hosts a biennial art festival that attracts visitors every second summer.

    In context

    The association holds a biennial conference to review long-term strategic goals, ensuring members meet every two years to discuss progress.

    Pitfall
    The biannual festival happens every two years. The biennial festival happens every two years.

    Use 'biennial' for every two years; 'biannual' means twice in one year.

    every other year
  2. 02 C2 Proficiency Technical Science

    adj.lasting for a period of two years.

    adj.having a duration of two years; specifically used in biology to describe a life cycle.

    Simple

    The scientist studied the biennial life cycle of certain forest insects.

    In context

    The research project focused on the biennial growth patterns of specific alpine shrubs that remain dormant during their first winter.

    two year
  3. 03 C1 Advanced Technical Science

    n.a plant that takes two years to grow, flower, and then die.

    n.a plant that completes its biological life cycle in two years, typically flowering in the second year.

    Simple

    Carrots are a common biennial, though we usually harvest them in their first year.

    In context

    Gardeners often plant biennials like foxgloves in consecutive years to ensure they have blooms every summer.

  4. 04 C1 Advanced Formal

    n.an event, like an art show or sports competition, that happens every two years.

    n.an event that recurs every two years, most commonly used in the context of international art exhibitions.

    Simple

    She was invited to show her paintings at the Venice Biennial.

    In context

    The city's photography biennial has become a major draw for international critics since its inception a decade ago.

Biennial sweet clover was also planted instead of the intended annual type, while fall rye persisted into the second year.

Phys.org· 1 Sept 2026

Meanwhile, India’s biennial forest report was due in 2025.

The Guardian· 25 Aug 2026

Borrowed from Latin bienni(um) (“two-year period”) [from bis, bi- (“twice”) + annus (“year”)] + -al (suffix forming adjectives). By surface analysis, bi- + -ennial.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Level C1 · Advanced
Frequency Frequent
Updated