[] () 99.999 per cent, which is the percentage of the time that some computer systems are expected to work properly 五个九（即 99.999%，某些计算机系统预计的正常工作时间）◆Most telephone companies are able to offer the five nines—or 99.999% reliability. 大部分电话公司能够提供“五个九”或者说 99.999% 的可靠性。◆a server with five nines availability 具有“五个九”可靠性的服务器