but表示完全的转折,程度比while要强烈的多试比较:The soles are leather, while the uppers are canvas. 鞋跟是皮的,而鞋面是帆布的。 he said it's wrong, but it's right actually. 他说这是错的,但这确实是对的。
while有对比之意如 I am watching TV while my sister is listening music.