信封的英文：
envelope

A packet of envelopes
一扎信封

This is a buff envelope.
这是张牛皮纸信封。

I slit the envelope open
我撕开了信封。

Fold the letter (in two) before putting it in the envelope.
把信(对)折起来再装入信封。

How intolerable the crested paper is
那花里胡哨的信封，真俗气。

I make some rough calculation on the back of an envelope.
我在信封背面做了一些估算。

He glanced at the envelope and recognized his uncle's handwriting.
他瞥了一眼信封，认出了他叔叔的笔迹。

Please enclose a self-addressed envelope
请在里面附一个写作你自己地址的信封。

He opened the bulky envelope first to skim the typewritten pages.
他首先打开那只厚实的信封，翻了翻那份打字文件。

His hand went into his pocket and a forefinger felt its way under the flap of the envelope, ripping it open in jerks
他把手伸进兜里，一只食指摸索到信封的口盖，分几截把信扯开了。