[误] I think it is an useful English dictionary.?

[正] I think it is a useful English dictionary.?

[析]在不定冠词 a与 an的用法中要注意的一点是： an用在以元音开头的词之前;而 a则用在以辅音开头的词之前。要特别注意的是以 u字母打头的单词，如 useful, university等，其第一个音标是[ j]，所以要特别予以注意。

[误] I need a hour to finish this letter.?

[正] I need an hour to finish this letter.?

[析]要注意 hour和 honest的第一个字母不发音。

[误] My teacher is a unknown man, but he is a very good man.?

[正] My teacher is an unknown man, but he is a very good man.?

[析]要注意以 u打头的单词，它的发音为[?]时，单数名词前要用 an，如 uncle等。

[误] There is a" f" in the word" football".?

[正] There is an" f" in the word" football".?

[析]英文字母单独使用时，如其第一个发音是元音时，其前面的不定冠词应该用 an而不是 a.

[误] I have a little brother. He is a 8 year old boy.

[正] I have a little brother. He is an 8 year old boy.

[析]要注意这些字母的第一个发音为元音，如 eight, eleven等。

able

[误] This bike is able to be repaired.?

[正] This bike can be repaired.?

[析] be able to主要表达某事或某人具有某种能力去作某事，应译为"有本领"、"有能力"、"可以"作某事，如： I'm able to swim across this river. 而 can可以用来表示具有接受能力或吸收能力。如： This radio can be repaired here.

about

[误] This class is about to begin just now.

[正] This class is about to begin.

[析]要注意 be about to是"将要"的意思，含有将来时之意，不要与表示过去时的时间状语连用。另外， be about to一般用作书面语，对应的口语是 be going to.

about on

about与 on都可以作"关于"讲，但却有所不同，例如： This book is about physics. 应译为"这是一本关于物理学的科普读物。"而： This book is on physics.则应译为"这是一本物理学方面的专著。"

above

[误] The temperature is five degrees over zero.?

[正] The temperature is five degrees above zero.?

[析]表达"在……上方"时， above与 over是可以互换的，如： The sky is above( or over) our heads. 但是要表达在垂直方向上的上方时则应用 above不可用 over，如： The sun has risen above the horizon.?

[误] There is often thick cloud above the South of China in summer.?

[正] There is often thick cloud over the South of China in summer.?

[析]当表达覆盖之意时，只可用 over而不能用 above.?

[误] There is a bridge above the river.?

[正] There is a bridge over the river.?

[析]用来表达"从……上方越过"时不能用 above只能用 over，如： The plane flew over the city. 但要注意 There is waterfall above the bridge. 则应译为"在桥的上游有一个瀑布。"

across?

[误] He ran across the wood.?

[正] He ran through the wood.?

[析] across是指某一动作在一平面内进行，而 through则是指该动作在一三维立体空间的运动过程。如： The man came in through the window. He walked across the square.

across?

across的主要用法有两个。其一，意为"对面"，如： There is a school just across the street. 其二，意为"横过"，如： He walked across the street.?

afraid?

[误] I dont't afraid of him.?

[正] I am not afraid of him.?

[析]要注意"害怕" afraid一词在英语中不是动词，而是形容词，要与 be动词连用。?

after?

[误] Two weeks after he left.?

[正] Two weeks later he left.?

[正] He left after two weeks.?

[析]要表达"在多少时间之后"，英语中有两种表达法，即：用 later时，要时间在前，如 three hours later;而用 after时要时间在后，如 after three hours.?

[误] My father will be back after a few hours.?

[正] My father will be back in a few hours.?

[析] 受中文的影响，这个介词常常被误用。当你要表达在一段时间内某个动作可以完成时，一定要用 in，而不能用 after，因为 after是指在某一时间之后。例如： This work will be done in two days. 即表明在两天内这一工作一定会做完。而如用了 after，即表示在两天之后，完成的时间是不确定的。