in a day和on a day區(qū)別主要在于：意思不同。in a day指的是在一天內(nèi)；on a day指的是在某一天。如：There are only so many hours in a day.The children were on a day's outing from school。

in a day雙語例句

1、There is no limit to how much fresh fruit you can eat in a day.每天食用多少新鮮水果都可以。

2、Don't let the defeat dishearten you!Remember that Rome was not built in a day.不要因為失敗而灰心！要知道成功不是一蹴而就的。

3、We can finish that little bit of work in a day.那么點兒工作，一天就可以干完了。

on a day雙語例句

1、When you have made up your mind,pick on a day when you will not be under much stress.你什么時候下決心了，就挑一個壓力不大的日子。

2、When I am on a day off sick--I'm always sick.我請一天病假——我總是生病。

3、It was on a day in early summer that the goose eggs hatched.初夏的某天，小鵝們被孵出來了。