Biennially

Biennially is an adverb describing something that occurs once every two years, or lasts for two years. The related adjective is biennial, and the related noun is biennium, a two-year period. The term comes from Latin bi- meaning two and annus meaning year, via French and Middle English.

Common uses describe events, reports, or budgets planned on a two-year cycle: a biennial conference, a biennial budget, a biennial report. In botany, biennial refers to plants that complete their life cycle in two years, typically with vegetative growth in the first year and flowering in the second, followed by death.

Be careful with biannual (or semiannual), which means twice a year. If you mean every two years, prefer biennially or biennial; if you mean twice within a year, use biannually or semiannually.

Examples: The festival is held biennially. The government publishes a biennial budget report. The plant is a biennial species.