if词性：if可作连词和名词两种词性。当if作为连词时，含义为“如果”、“假若”、“无论何时”、“每次”，可与will或would连用，表示客气地请求；当if作为名词时，含义为“不确定的情况”。
if的基本释义及用法介绍
if可作连词和名词两种词性，意为如果;假若;倘若;当;无论何时;每次;不确定的情况。可与will或would连用，表示客气地请求。例句有：
1、If you see him, give him this note.
你要是见到他，就把这个便条给他。
2、They would have been here by now if they'd caught the early train.
假若他们赶上了早班火车，现在就该到这里了。
3、She glares at me if I go near her desk.
我一走近她的办公桌，她就对我瞪眼。
4、If you will sit down for a few moments, I'll tell the manager you're here.
请稍坐，我这就告诉经理说您来了。
5、I wonder if I should wear a coat or not.
我不知道该不该穿外套。
6、I'd be grateful if you would keep it a secret.
你如果能对此保密，我将不胜感激。
7、If she has any weakness, it is her Italian.
如果要说她有什么缺点，那就是她的意大利语不大行。
8、He's a good driver, if a little over-confident.
他是个好司机，虽然有点过于自信。
9、If you think about it, those children must be at school by now.
想想吧，那些孩子现在一定在学校了。
10、If I may make a suggestion, perhaps we could begin a little earlier next week.
我来提个建议吧，或许我们下个星期可以早一点开始。
11、There are still a lot of ifs and buts before everything's settled.
在一切得以解决之前还有很多不定因素。
12、If he wins─and it's a big if ─he'll be the first Englishman to win for fifty years.
假设他赢了——不过这还是个很大的疑问——他将成为五十年以来第一个获胜的英格兰人。
