1. They celebrate their wedding anniversary annually.
    他们每年庆祝一番结婚纪念日。

1. 每年：annual 一年一次的 | annually 每年 | annuity a compound interest 复利年金

2. 每年地：generously#宽大地 | annually#每年地 | virtually#几乎

3. 年度,每年：warrant 使有(正当)理由,保证 | annually 年度,每年 | canvass 兜售,销售

4. 年年,每年：centennial 百年纪念 | annually 年年,每年 | centenarian 百岁或逾百岁以上的人

1. without missing a year

    e.g. they travel to China annually

    Synonym: yearlyevery yeareach year

2. by the year
    every year (usually with reference to a sum of money paid or received)

    e.g. he earned $100,000 per annum
           we issue six volumes per annum

    Synonym: per annump.a.per yeareach year