1.yesterday的基本意思是“昨天”,指今天的前一天。
2.the day before yesterday是“前天”的意思,其中的定冠词the不可以省略。

Yesterday was Sunday.昨天是星期日。
Yesterday was a beautiful day.昨天是个好天气。
Where's yesterday's paper?昨天的报纸在哪里?
Is that yesterday's newspaper?那是昨天的报纸吗?
I saw him at yesterday's meeting.在昨天的会议上我见到了他。
I can remember it as if it were yesterday.我对此事记忆犹新,恍如昨日一样。
Where were you yesterday morning?昨天上午你在什么地方?
He left yesterday afternoon.他昨天下午离开了。
They arrived yesterday morning.他们是昨天上午到达的。
She came to tea the day before yesterday.她前天来吃过茶点。

下面两个短语意思相同:
yesterday's morning
yesterday morning
昨天早上

1.我昨天整天都呆在家。
［误］  I stayed at home all yesterday.
［正］  I stayed at home all day yesterday.
［正］  I stayed at home for the whole of yesterday.
［析］  作“昨天一天”解时,不能说all yesterday,这不合乎英语的习惯表达法,应该说all day yesterday或for the whole of yesterday。
2.昨天晚上我们去看电影了。
［误］  We went to the cinema yesterday night.
［正］  We went to the cinema last night.
［正］  We went to the cinema yesterday evening.
［析］  习惯上可以说last night或yesterday evening,但不能说yesterday night。但是,我们可以说yesterday morning〔afternoon〕(昨天早晨〔下午〕),而不说last morning〔afternoon〕。

1.yesterday用作副词时意思是“在昨天,在昨日”,强调的是某事发生的时间。
2.yesterday通常不可以放在主语和谓语之间。

用作状语
He arrived only yesterday.他昨天刚到。
I wasn't born yesterday.我不是小孩子。
I thought yesterday that he would be here in no time.我昨天想他不久就会来了。
She was very busy yesterday.昨天她非常忙。
We had no school yesterday.我们昨天没上学。
用作表语
It was only yesterday that I saw him.我昨天才看见他。

1.我昨天遇见了他。
［误］  I met him on yesterday.
［正］  I met him yesterday.
昨天祖父从楼梯上跌下来了。
［误］  On yesterday grandfather fell downstairs.
［正］  Yesterday grandfather fell downstairs.
［析］  一般在yesterday, tomorrow, last night等词前不加介词。
2.他写信告诉我说他日前去看望过她。
［误］  He wrote to tell me that he had visited her yesterday.
［正］  He wrote to tell me that he had visited her the day before.
［析］  在间接引语中一般用the day before替代yesterday。
3.我昨天看了这出戏。
［误］  I have seen the play yesterday.
［正］  I saw the play yesterday.
［析］  yesterday只能修饰过去式的谓语动词,而不可修饰现在完成式的谓语动词。

［词源］  ＜古英语geostran dæg(昨天,昨日)