The letter was written in very formal language.

这封信使用了非常正式的语言。

First, formal language tends to be more polite.

首先，正式语言显得更礼貌。

Second, speechmaking requires more formal language.

其次，公开演说需要使用正式语言。

It's a formal language that remains easy to read and write.

这就是一种读起来和写起来都很轻松的规范语言。

A formal language schema, expressed in RELAX ng compact syntax.

一个规范的语言方案，以RELAX NG压缩语法表达。