1. 在下列情况，其后通常不接介词 into：

(1) 表示进入某一具体的东西时：

The train entered the tunnel. 火车进入隧道。

She entered the room without knocking. 她没敲门就进了房间。

The bullet entered his head. 子弹射入他的头部。

(2) 表示进入某一组织或某一机构时：

He entered the army last year. 他去年参军了。

Then he entered a famous university. 后来他进了一所名牌大学。

(3) 表示报名参加考试(比赛等)时：

All his friends entered the examination (race). 他所有的朋友都报名参加了考试(比赛)。

She not only entered the competition she actually won it! 她不但参加了竞赛——而且居然获胜了!

Although he had only entered the contest for fun, he won first prize. 尽管他参加这次竞赛只不过是闹着玩儿而已，却赢得了头奖。

2. 下列情况，enter 后通常接介词 into：

(1) 开始(做某事)

I dared not enter into conversation with him. 我未敢与他交谈。

He entered into business at the age of 25. 他25岁时开始经商。

(2) (开始)讨论，研究，处理

Let’s enter into the subject of taxes. 咱们来讨论一下税款问题。

We need not enter into details. 我们不必讨论(研究、处理)细节。

(3) 积极参加，参与，投入

He entered into our plans with terrific zest. 他满腔热情地参加了我们的项目。

The party was successful because everyone entered into the spirit of the thing. 这次聚会因大家积极参与所以很成功。

(4) 达成(协议)，缔结(条约)

We entered into a solemn bond. 我们缔结了一项正式协定。

You shouldn’t enter into contract until you have studied its provisions carefully. 你应该先仔细研究合同的条款，然后再签订。

(5)(不用于被动语态)形成某事物的一部分：

This possibility never entered into our calculations. 我们从未考虑过有这种可能性。

Flour has largely entered into their diet. 面料已成为他们的主食之一。

(6) 懂得，领略，体会，理解：

He didn’t enter into her mood. 他不体谅她的心情。

I can enter into your feelings at the loss of your wife. 我能理解你失去妻子后的心情。

(7) 表示进入某具体东西且强调深入其内时(若不强调则可不用)：

The arrow entered into his head. 箭射进了他的头。

We entered into a woody mountain. 我们进入了一片山林里。