一、compare与contrast的误用
我们先从两者的定义入手来看两者的区别。 Compare的定义为：to examine people or things to see how they are similar or different. Contrast的定义为：to compare two or more things to show the difference between them.由定义不难看出前者侧重于找到两个或多个事物的异同,而后者则侧重于它们的不同。
看个例句：It is interesting to compare their situation to ours./It is interesting to contrast their situation to ours.
前一句翻译为：对比一下我们的情况与他们的情况会很有趣。后一句的翻译为：我们的情况与他们的情况有很大的不同,这很有趣。
再看一个引自OXFORD ADVANCED LEARNER’S DICTIONARY的例子：There is an obvious contrast between the culture of East and West.The company lost $7 million in contrast to a profit of $6.2 million a year earlier. When you look at their new system, ours seems very old-fashioned by contrast.
不难发现,Compare翻译为“与……相比”而contrast可译为“明显不同的是……”,切记这种翻译方式就不会用错彼此了。

二、介词使用错误
1. 普通介词的误用
一般表现为固定搭配错误,如常把provide sb. with sth.用成provide sb. sth.; be satisfied with用成be satisfied for等等,虽然这样的错误看似无伤大雅,但在考官眼里就是影响顺畅阅读的,当然会影响最终成绩。解决的办法简单而古老：把常见的固定搭配牢记于心,问题自然就解决了。
2. “to”作为介词的误用
“to”最常见的用法是以动词不定式符号的形式出现的,所以同学们也已经习惯了“to do”的固定搭配。对于一些如walk to me, to the left等介词to表方向等常见用法一般也不会出现错误。但是对于与动词搭配的介词to就会经常犯错，如：
More and more students have taken to depend on their parents to make decision for them.
这里的‘take to’ means ‘to begin to do sth. as a habit’其中‘to’为介词,所以后面只能接名词或相当于名词的词,如动名词。所以上面句子中的‘depend on’应改为“depending on”。“take to”的另一个常用用法也需要牢记：
He hasn't taken to his new school. (这里‘take to’ means ‘to start liking sb. or sth.’)
Prefer A to B中的“to”也是介词,会有prefer doing sth. to doing sth./ prefer sth. to sth. else,“prefer to do sth. rather than do sth.”中的“to”可是真正的不定式符号。
类似的常用用法请同学们牢记：
Be used to doing/Be accustomed to doing/See to doing/Adapt to doing/Adjust to doing/prefer doing sth. to doing sth.等等,请注意平时仔细积累。

三、assume及claim使用不够准确
我们知道, think, assume, claim是议论文中常用引出观点的动词。在实际作文中,同学们往往认为几个词的意思是一样的,完全可以代换,所以拿过来就用。甚至还有同学把consider也拿过来与之混用。我们首先还是从定义来看这几个词的不同：
Think:to have opinion or belief about sth.
翻译为“认为”,通常接宾语从句来表达比较确定的观点。
Assume:to think or accept that sth. is true but without having proof of it.
翻译为“假设、假定”,是否有事实依据是不确定的。
Claim:to say sth. is true although it has not been proved and other people may not believe it.
翻译为“声称”,用这个词往往意味着不赞同紧跟其后的观点,所以很少用作‘I claim that…
Scientist are claiming a breakthrough in the fight against cancer, but in fact, …。
所以‘It is claimed that’通常翻译为“有报道称……”。和‘it is reported that ’的区别在于后者翻译为“据报道”,往往代表着作者赞同报告的内容,
Consider:to think about sth carefully, especially in order to make a decision
翻译为“考虑”,一般不用作引出观点,看个例子：
We are considering buying a new car.
所以,千万不要在托福写作的第一段(观点表达段)就因为用词把握不准而导致对整篇文章的低分印象。

四、表“建议”的词汇后面忘记用虚拟从句
这是摘自学生托福作文中的一个病句：
I suggest he continues his study instead of working after graduation from high school.
因为‘suggest’翻译为“建议”,所以后面的从句应该用虚拟语气,黑体部分应该改为“(should) continue”
所以考生一定要牢记以下常见表“建议”的词汇,而且要记住这些词接从句时要用虚拟语气：Recommend, suggest, advise

五、such as与for example的混用
我们知道,在表示举例子的时候,such as与like是完全等同的,如：Wild flowers such as/like orchids and primroses are becoming rare.
但是同学们对于Such as、for example的把握还是不够准确。我们都知道,后者接句子前者接词语表示举例子。于是就有了下面的写法：
There is a similar word in many languages, such as in French and Italian.
这里的such as改为for example为好,因为“in French and Italian”其实是“there is a similar word in French and Italian”的简化,所以要用for example来引出例证。

以上就是这样。类似这样的词汇还有很多，大家在托福备考过程中，一定要多加总结和积累，有效区别这些词汇。