A topic is a particular subject that you discuss, study, or write about.
近义词
subject , matter , theme
双语例句
例： The weather is a constant topic of conversation in Alaska.
在阿拉斯加，天气是一个永恒的交谈话题。
例： The main topic for discussion is political union.
讨论的主题是政治联盟。
例： This topic is explored more fully in chapter 5.
第五章更完整地探讨了这个主题。