It's a letter

字母───letter;表达───expression

I told her to send the letter by airmail.───我叫她把那封信寄航空.

I wrote him a letter to acknowledge the receipt of the book he sent me.───我给他写了一封信,表示收到了他寄来的书.

She guessed that the letter had something to do with her husband.───她猜想这封信与她丈夫有关.

You may apply for tickets in person or by letter.───需要票者可亲自来申请亦可来信索取.

The letter instructed him to report to headquarters immediately.───那封信指示他立即向总部汇报。

A letter of introduction will ensure you an interview.───凭一封介绍信准保会接待你.

I had no reply to my letter.───我没有收到回信.

I folded the letter and then put it into the envelope.───我把信折好后放进信封里.

The letter is ready for the post.

I consigned her letter to the waste basket.

You should apply in person / by letter.

I have received a letter from my brother.

His letter was completely without punctuation.