对某人有好感不但是一种非正式用法，而且它更多涉及的是年轻人。

Not only is crushing on someone informal, it is more likely to involve young people.

youdao

道再见的非正式用法是See you later(再见)。尤其在你希望很快再见到某人时使用这种用法。

An informal way of saying goodbye, especially if you expect to see the person again quite soon, you can say: see you later.

youdao

因为这意味着除了文化含义和习惯之外，译员还对俚语和其它非正式的用法非常熟悉。

That means the translator is familiar with slang and other informal usage, as well as cultural meanings and habits of those who'll read what's produced.

youdao

But it's not at all unprofessional.

但这并不是完全非正式的用法。

Is it okay 课堂 - SpeakingMax英语口语达人