We received a letter of apology.

我们收到了一封道歉信。

《牛津词典》

The first letter of a phrase or song refrain.

避免用一个词组或一首歌名的首字母。

youdao

Essentially, Soundex algorithms function by mapping each letter of a given alphabet to a numerical code representing its phonetic group.

从实际上说，soundex算法的运作方式是把某个字母表中的每个字母映射成代表它的语音组的一个数字代码。

youdao

Bouchat faxed the design to the Maryland Stadium Authority before the team name and logo were revealed suggesting its use for the new team formerly the Cleveland Browns and expecting compensation in the form of a letter of recognition and a signed helmet should the logo be used.

FORBES: Connect

Any salvaging that took place may have happened as a result of the reader composing a letter, often of a confessional nature.

ECONOMIST: Esther Lederer, agony aunt, died on June 22nd, aged 83

For years, the Commission's reaction to made-up stories (eg, the EU is to scrub all mentions of the Queen from British passports) has been to write a polite letter of correction, and after a delay of some days, put a little item on its website.

ECONOMIST: European politics