关键时刻或紧要关头用常规的英语表达可以是“ the critical/crucial moment"，例如：critical moment:You must think twice and watch your step at this critical moment.关键时刻，你可不能犯糊涂。crucial moment:He wasn't there at the crucial moment.紧要关头他却不在那里。
类似的还可以用两个习语 come to a head 或 in the nick of time 来表示，例如：1. come to a head，字面是”上头了“，比喻达到很重要的时刻，可以译为”紧要关头，关键时刻“，例如：The investigation came to a head last week when my colleague was found guilty of fraud.上周我的同事被判犯有欺诈罪，调查进入了关键时刻。解析：find + sb/sth + 宾补（形容词） 表示发现某人或某事怎么样，又如：Some people find it difficult to discern blue from green.有些人难以鉴别蓝绿两种颜色。The battle between the two factions of the city's leading sport club came to a head today.这座城市主要体育俱乐部的两派之争今天达到了危急关头。2. in the nick of time，字面意思是”时间的缝隙“，比喻紧要关头，可以译为“在最后一刻，紧要关头，恰是时候”，例如：He arrived at the wedding in the nick of time.他及时赶到了婚礼现场。The ambulance arrived in the nick of time. If they had been 5 minutes later he would have died.救护车及时赶到了。如果是晚5分钟到，他就会死了。His speech was delivered in the nick of time. I was beginning to think that the people were going to start fighting.他的演讲在紧要关头发表了。我开始觉得人们要开始战斗了。You cannot keep arriving in the nick of time. Make sure to check your watch tomorrow so that you can be early enough to help.你不能一直在最后一刻赶到。明天一定要看表，这样你就可以早点来帮忙了。
