It is biennial.
Biennial -sg that happens every alternate year.
Biennial means "occurring every two years," OR "lasting for two years." The word biannual can also mean "occurring every two years," although its most common meaning is "occurring twice a year."
Annal
The adjective is quadrennial. (extension of 1-annual, 2-biennial, 3-triennial) (The archaic word for a five-year period is a lustrum.)
Year 1000 was a medieval word. It was approximately in the middle of the Middle Ages. It starts with the letter Y.
It is biennial.
biennial
bi-ennial
Biennial -sg that happens every alternate year.
annual or anniversary
You could refer to it as a quarterly event.
Biennial means "occurring every two years," OR "lasting for two years." The word biannual can also mean "occurring every two years," although its most common meaning is "occurring twice a year."
Biennial. A biennial event, such as a conference or festival, happens every two years.
Bi, means 'every other'. For example: Bi-weekly, Bi-monthly, Bi-Anually
Biannual. Biannual can mean occurring every two years, OR occurring twice a year. Biennial, on the other hand, means only the former: occurring every two years.
The prefix "bi-" means occurring twice in a given period. Therefore, a word that signifies happening twice a year could be "biannual."
Bellis perennis is the Latin equivalent of 'English daisy'. In the word by word translation, the adjective 'bellis' used as a noun means 'beautiful, pretty'. The adjective 'perennis' means 'occurring every year, each year over a period of two or more consecutive years'.In contrast, the ox eye daisy draws on the Greek equivalent of Chrysanthemum leucanthemum. In the word by word translation, the Greek combined word 'chrysanthemum' means 'golden flower'. The Greek combined word 'leucanthemum' means 'white flower'.