1、高中英语知识点大全（92）：once1、on the air/in the air/by air/in the open airon the air 表示(用无线电、电视)播送节目。如：Whats on the air this evening? 今晚的广播内容是什么？These programmes come on the air everyday. 这些节目每天广播。其反义词为go off the air“停止广播”。如This radio station goes off the air at midnight.这家广播电台于午夜停止广播。in the air 表示“在空中、在流传中、（
2、问题，计划等）悬而未决（未确定的）、充满了（某种）气氛”。如：There was dampness in the air. 空气潮湿。The plan is quite in the air. 这个计划还很渺茫。The Spring Festival was in the air for weeks before. 几周前就充满了春节的气氛。Bofore the matter was publicly announced, it had long been in the air.这件事在公诸于世之前早就传得满城风雨了。by air 表示“乘飞机、由航空”。如He went to Shangha
3、i by air. 他乘飞机去上海.in the open air 表示“在户外、在露天里”。如：People love life in the open air. 人们喜欢露天生活。2、once1）意为“曾经”时，侧重“有一次”的意思，是副词在句中做状语，如：Once he owned a large house. 他曾经拥有一所大房子。注意：once与ever的区别ever常用于疑问句，有时可用于过去分词前，多在完成时态中。在句中可译为“曾经”，有时不需翻译。如：Have you ever been there? 你去过那儿吗？The largest tree ,ever found th
4、ere ,is one about 500 years old.那儿发现的最大的树有大约500年树龄了。2）意为“一旦”时，用作连词引起从句。如：Once you go there,buy a book for me.Once you began, you couldnt stop. 一旦开始，你就不能停。Once you object to a man, everything he does is wrong. 一旦你反对一个人，那么他做的一切都是错的。对比：once 强调条件意味；as soon as 强调时间的紧接As soon as you come to Beijing, pleas
5、e let me know. 你一来北京就请告诉我。3、on the point of该短语常在句中作表语，意为“正要（去做某事）”，意思相当于be about to do sth.。如：We were on the point of calling him up when he came.对于point名词应掌握它的用法如下：if/when it comes to the point 如果/当时机到来（时）如：When it comes to the point,he refused to help.from sb.s point of view 从某人的角度来看如：Try to look at school from the childs point of view.
