for a second time和for the second time这两个意思上完全不一样，举个例子比较就很清楚1. for a second time，再次，又一次（不一定是第二次）I have been China for a second time this year.今年我又去了一次中国。今年去了两次，但也许去年，前年，十年以前，也去了。2. for the second time，第二次I have been China for the second time this year.今年是我第二次去中国。出生后只去过两次，今年第二次。
