n.白天；一天；时代

Owls sleep by day and work at night. 猫头鹰白天睡觉晚上工作。

There will be occasional showers during the day. 白天将偶有阵雨。

He is seldom at home during the day. 他白天很少在家。

You can see stars by night, but not by day. 你在夜晚可以看到星星，白天却看不到。

He has been working all day. 他已工作了一整天。

The milkman comes every other day. 送牛奶的人每隔一天来一次。

He is the man of the day. 他是时下的风云人物。

He was a great singer once but now he's had his day. 他曾是个红歌星，但现在风华已去。

day的基本意思是“一天”,指二十四小时长的一段时间,是可数名词。也可指“日间,白天”,既可用作可数名词,又可用作不可数名词,通常不加冠词。

day也可表示“工作日”,指一天二十四小时之内的工作时间,是可数名词。

day还可作“时期; 时代; 寿命”解,常用复数形式,若用单数常须与my, their等物主代词连用。

day还有“全盛时期,黄金时代”的意思,是单数名词,不用于复数形式。

day间或表示“胜利,竞争,战斗”,是不可数名词,前面接定冠词。

Day常用在表示法定的或宗教节日的短语中,其前不加冠词。

day可用作量词, a day可表示“每天”。

当定语从句所修饰的词是day时,关系词that/when/which多省略。例如:His father died the day when he was born.他父亲在他出生那一天去世了。

day and night和night and day,有的词典认为两者意思有些不同:day and night等于continuously,用于以昼为主的场合, night and day等于always,用于以夜为主的场合,实际上,两者现已无区别地使用,都是“日夜不停地,日日夜夜地”的意思。

the day before yesterday(前天), the day after tomorrow(后天)等这些短语里的the在美式英语中可以省略。例如:He left for London (the) day before yesterday.他前天启程去伦敦了。