noun
A straightforward loanword used in modern Japanese for anniversaries, often in commercial or event contexts.
今日は結婚10周年のアニバーサリーです。
Today is our 10th wedding anniversary.
アニバーサリーイベントに参加しませんか？
Would you like to join the anniversary event?
記念日 is the native Japanese term for 'anniversary' or 'memorial day', used more broadly and formally. アニバーサリー is a loanword with a slightly more modern, commercial, or celebratory feel.
Borrowed from English 'anniversary'.