Definition
Occurring twice a year. In aviation usage, the term is sometimes applied loosely, but its strict meaning is two events per year (every six months).
Plain English
Happening twice in one year.
Context Anchor
Seen in maintenance, inspection, training, and recordkeeping discussions when a requirement or event repeats during the year.
Derivation
From Latin 'bi-' meaning 'two' and 'annus' meaning 'year.' Literally: two times a year. Knowing the root makes the distinction from 'biennial' (every two years) easier to remember.
Why Pilots Care
Biannual and biennial are often confused, and the difference matters. The FAA flight review required by 14 CFR 61.56 is a biennial flight review -- once every 24 months -- not biannual (twice a year). Mixing them up can lead to misunderstanding currency requirements.
Intuition Check
Biannual does not mean every two years here. It means twice each year.
Example Sentence 1
The shop performs a biannual calibration on the test equipment, once in spring and once in autumn.
Example Sentence 2
Maintenance tracked biannual checks on the aircraft systems.