There are all kinds of reasons why languages die. One is the physical reason when people are affected by famine and disease and earthquake. Another is genocide, when some countries deliberately try and stamp out a small language. But the main reason is globalization. That is, there are some huge languages in the world, like English and Arabic and Spanish and French, and these are like steam rollers crushing the smaller languages that they find in their path.
A great deal can be done to preserve an endangered language. The first thing is that the people themselves must want the language to be preserved. That’s very important. The second thing is the powers-that-be must want the language to be preserved. They must have a respect for the minority languages that are in their care. And the third thing that has to be there, of course, is cash. It costs quite a lot of money to preserve an endangered language. Think about it, you have to train the teachers, you have to write books for the children. And all that sort of thing. It doesn’t cost an extraordinary amount of money, but it does cost a bit. So without money, endangered languages don’t have a positive future.
4.die out 灭绝；消失
5.in the course of