But、While、However都有而的意思。But ：例：She looks very young, but she is already in her 30's. 她看上去很年轻,然而她已三十多岁了While：例：While the south of the country grows richer, the north grows poorer.南部越来越富，而北部却越来越穷。However：例：This experiment, however, has its fair share of controversy and detractors.然而，这个实验，却引起好多争论与不满but表转折,表示前后两个事实相反. while更偏向于作对比.
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