信封 :

envelope

Relative explainations:

Examples:

1. 这个信封封得很严实。

The envelope was firmly sealed.

2. 寄信前，他在信封上写上地址。

He addressed the envelope before mailing the letter.

3. 信封内装有几份附件。

There are several enclosures in the envelope.

4. 他用蒸汽把信封上的邮票揭下来。

He steamed the stamp off the envelope.

5. 我用了一个邮资已付的信封。

I use a prepaid envelope.

6. 他把邮票贴在信封上。

He glued a stamp onto the envelope.

7. 信封（的封口）没粘住.

The (flap of the) envelope was unstuck.

8. 这个信封开了.

This envelope has come unstuck.