As adverbs the difference between halfyearly and biannually
is that halfyearly is while biannually is twice per year.
As an adjective halfyearly
is .
biannually
English
Adverb
(-)
Twice per year.
Usage notes
* Some authorities report confusion between biennially and biannually. Using "semiannually" may reduce the risk of confusion.
Synonyms
* semiannually