informal是什么意思？

Just because emails are a quick form of communication, it doesn't mean emails, especially business emails, should be written using informal, shortened forms of words.

Museums and other institutions of informal learning may be better suited to teach this skill than elementary and secondary schools.

Make full use of informal learning resources.

Informal learning environments tolerate failure better than schools.

For that, we have a robust informal learning system that gives no grades, takes all comers, and is available even on holidays and weekends.

It has a very informal atmosphere, quite unlike some grand houses you visit.

Its informal conversational style would make interaction comfortable, and yet the machine would remain slightly unpredictable and therefore interesting.