Note that discuss is never used as an intransitive verb. You cannot say, for example, 'They discussed', 'I discussed with him', or 'They discussed about politics'. Instead, you can say that you have a discussion with someone about something. I had a long discussion about all this with Stephen. You can also add an object and say that you discuss something with someone. If the discussion is less formal, you can simply use the verb talk. They come here and sit for hours talking about politics... We talked all night long.

注意 discuss 从不用作不及物动词。例如，不能说 they discussed，I discussed with him 或者 They discussed about politics。但可以说 have a discussion with someone about something。如：I had a long discussion about all this with Stephen（我和斯蒂芬就这一切进行了一次长谈）。还可以在 discuss 和 with 之间加宾语，可说discuss something with someone。如果谈话不是很正式，用talk就可以了。如：They come here and sit for hours talking about politics（他们来这儿一坐几个小时谈论政治），We talked all night long（我们彻夜长谈）。