
She believes she will be famous one day.
= She believes she will be famous someday.
(她相信她有一天會很有名。)
(此時one day = someday,因為是未來的事)
Someday you’ll know what it’s like to be a parent.
= One day, you’ll know what it’s like to be a parent.
(有一天你會知道為人父母的感受。)
(此時one day也等於someday,因為仍是未來的事)
I ran into a high school classmate one day.
= One day, I ran into a high school classmate.
(有一天我巧遇高中同學。)
(此時就只能用one day,因為是過去的事)