sure與certain的用法與區(qū)別
一、兩者在用法上的相同點
兩者都可用作表語，表示“一定”或“確信”，有時可互換?；Q的場合應注意以下幾點用法：
1. 表示說話者的態(tài)度或看法
即表示說話者自己的態(tài)度或看法，其意為“一定會”“肯定會”。此時主要用法有：
(1) 單獨用作表語。如：
One thing was sure [certain]: they'd be late. 有一件事是確定無疑的，他們會遲到。
(2) 后接不定式。如：
He's certain [sure] to win. 他一定會成功。
They're certain [sure] to need help. 他們肯定需要幫助。
If you do this, you are certain [sure] to be found out. 如果你這樣做一定會被發(fā)現(xiàn)。
2. 表示句子主語的判斷或信念
即表示句子主語對某一情況的判斷或信念，其意為“相信”“確信”“有把握”等。此時通常用于以下結構：
(1) 后接of [about] sth。如：
He is certain [sure] of success. 他確信會成功。
Are you certain of [about] that? 你對此有把握嗎?
(2) 后接 of doing sth。如：
Our team is certain [sure] of winning. 我們隊有把握贏。
You can be sure [certain] of his agreeing. 你可以放心他會同意。
比較同義句：
He is certain [sure] of winning.
=He is sure [certain] that he will win. 他自信會贏。
(3) 后接 that / whether / if 從句。如：
I am sure [certain] that he is honest. 我肯定他是誠實的。
I'm sure [certain] that it's not your fault. 我敢肯定這不是你的錯。
Are you certain [sure] that this is the right road? 你肯定這條路對嗎?
注：當be sure [certain]為肯定式或疑問式時，后接that從句；當be sure [certain]為否定式時，后接whether [if]從句。如：
I'm not sure [certain] whether he still works there. 我不能肯定他是否還在那里工作。
I wasn't sure [certain] whether he would agree. 我不太肯定他是否會同意。
He wasn't sure [certain] whether he would be able to get back in time. 他不能肯定他是否能準時回來。
(4) 后接其他從句。如：
I'm not sure [certain] where she lives. 我不能肯定她住在哪里。
I'm not certain [sure] who wrote it. 我不太清楚這是誰寫的。
二、只能用certain的情形
以下情況通常只用certain，而不用sure：
1. 當句中用了形式主語或形式賓語 it 時。如：
It's certain that he'll come tomorrow. 他明天肯定會來。
I thought it certain that he would be late. 我肯定他會遲到。
It's certain that prices will go up. 價格肯定會上漲。
It's not certain how much it will cost. 這要花多少錢還不確定。
2. 當表示“某一”“某些”時。如：
A certain Mr Green wants to see you. 有個叫格林先生的人想見你。
Certain plants are good to eat but others are not. 有些植物好吃, 而其他一些則不好吃。
三、只能用sure的情形
在 Be sure (not) to do sth.(一定要或不要做某事)這類祈使句中通常不用 certain。如：
Be sure not to forget it. 千萬別忘記啦。
Be sure to get there before nine. 務必在九點前到達。
Be sure to turn off the light when leave. 離開時一定要關燈。
四、兩者在習語中的用法
1. 用于 for certain / for sure, 意為“肯定地”“確切地”等，兩者可互換。如：
I can't say for certain [sure] when he will come. 我不敢肯定地說他什么時候來。
No one knows for sure [certain] what happened to her. 沒有人確切地知道她出了什么事。
2. 用于 make certain / make sure，意為“弄清楚”“弄得有把握”，兩者可互換。如：
They made certain [sure] (that) they weren't late. 他們有把握不遲到。
I think there's a train at 10:40, but you'd better make certain [sure] of it. 我想10:40有趟火車，但你最好去核實一下。