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daily; everyday
days (e.g. of one's youth)
every day; day after day; day by day; from day to day
「日日」 has another reading with different meanings.
日日の地道な努力が大切だと思います。
I think daily effort is important.
彼女は日日成長しているのがわかる。
You can see she is growing day by day.
日日の生活を大切に丁寧に過ごしたい。
I want to live my daily life carefully.