363　come in, come into和enter

1　come in 意为“进来”，单独使用，in 是副词，后面不接名词。

He was reading when I came in . 我进来时他在读书。

She didn't allow the stranger to come in . 她不允许那个陌生人进来。

2　come into 意为“进来，进入”，into 是介词，后面必须接名词。

Please ring the bell before you come into the room. 进入房间前请先按门铃。

We came into the hall one by one. 我们一个接一个进入大厅。

3　enter 也表示“进入”，正式用词，为及物动词，后面直接跟宾语。

The teacher entered the classroom with a book in his arm. 老师腋下挟着一本书走进教室。

She entered the university at the age of eighteen. 她18岁上了大学。