副詞
释义
未來不定指的時間；日後，以後；有朝一日
One day I shall upgrade my software, but not just yet.
之後我要升級我的軟件，但是不是現在。
過去不定指的時間；之前某日，有一天
One day I was playing with a girl from my class.
有一天，我正和同班的女生玩。
One day I was out in the barn and he drifted in. I was currying the horse and he set down on the wheelbarrow and begun to ask questions.
1913, Joseph C. Lincoln, chapter 11, in Mr. Pratt's Patients:仅按字面意思，并无比喻或俗语义；参见one、day。
You can stay one day or two.
你可以待一天或兩天。