Describes something that happens or is done once each year.
This event is held annually.
I set new goals every year.
semiannually; every six months
Standard kanji-kana mixed spelling.
Kanji spelling using 毎; less common but still seen.
Compound of 年 (toshi, 'year') + ごとに (goto ni, 'each, every'). The ごとに part derives from 毎 (goto) + particle に.