The fifth item in a series is the one that you count as number five.
Joe has recently returned from his fifth trip to Australia.
乔最近从他的第五次澳大利亚之旅归来。
fifths
A fifth is one of five equal parts of something.
India spends over a fifth of its budget on defence.
印度的国防支出占其财政预算的五分之一以上。