◆busy adj.
比较以下正误句型：
他非常忙。
正：He is very busy. / He is as busy as a bee.
误：He is as busy as a horse [cow, fish, bird, etc].
他在忙于写一本小说。
正：He is busy writing a novel.
误：He is busy to write a novel.
你工作忙吗?
正：Are you busy (with your work)?
误：Is your work busy?
◆buy v.
1. 用作动词，表示“买”，可带双宾语；若双宾易位，通常要用介词 for。如：
我叔叔为我买了本英语词典。
正：My uncle bought me an English dictionary.
正：My uncle bought an English dictionary for me.
2. 表示向某人买某物，通常用介词 from。如：
He bought this watch from a friend. 他从一位朋友那儿买了这块手表。
3. 表示用多少钱买某物，通常用介词 for。如：
I bought the computer for $600. 我花600美元买了这台电脑。
He bought it for very little money. 他买它只花了一点点钱。
注：有时也用介词 at, 侧重指价格。如：
He bought them for [at] 10p each. 他以每个10 便士的价格买下了它们。
4. 是终止性动词，因此在肯定句中不宜与一段时间连用。如：
这房子我已买了十年。
正：I bought this house ten years ago.
正：I have had this house for ten years.
正：It’s ten years since I bought this house.
误：I have bought this house for ten years.
◆by prep.
1. 表示方式，主要用法有：
(1) 与交通工具连用，表示“乘”、“坐”。如：
by bus 乘公共汽车 by bike 骑自行车
by train 乘火车by plane 乘飞机
by taxi 乘出租车 by ship 坐轮船
有时也与那些与交通工具密切相关的名词连用。如：
by air 乘飞机 by water 走水路
by land 走陆路 等
注：以上表达通常不用冠词，但是若表示交通工具的名词前插有定语，则可以用冠词。如：
We’re going by the 10:30 train. 我们坐10:30的火车去。
He went to Shanghai by a large ship. 他乘一艘大船去上海。
(2) 与抽象名词或表抽象意义的普通名词连用，表示“用”、“通过”等。如：
be electricity 通过电力 by experience 通过经验
by force 通过武力 by hard work 通过努力
by phone 用电话 by telegram 用电报
by letter 用信件by express 用快件
by air mail 用航空邮件by ordinary mail 用平信
by post 用邮寄 by radio 用无线电 by hand 用手工 by machine 用机器
注：以上表示通常不用冠词或其它限定词，但是：
by this means [method] 用这种方法
(3) 与动名词连用。如：
He makes a living by teaching. 他以教书为生。
Lock this door by turning the key twice to the left. 锁这扇门要把钥匙向左转两圈。
2. 表示计量单位，意为“以……计”，若后接单数可数，名词其前要用定冠词 the；若后接复数名词或抽象名词则通常不用冠词。如：
They are paid by the hour (by the month). 他们所得报酬按小时(月)计。
Are bananas sold by weight or at how much a piece? 香蕉是按重量出售，还是按多少钱一根出售?
The enemy came by the thousand [by thousands]. 敌人数以千计地扑来。
3. 表示抓住或握住某人或某物的某一部位，其中这个人或物应是前面已提到过的，且在介词 by 之后通常用定冠词 the而不用物主代词。如：
Suddenly she caught him by the ear. 突然间她抓住了他的耳朵。
The policeman took the thief by the hand. 警察抓住了小偷的手。
本文来自：逍遥右脑记忆 http://www.jiyifa.com/gaozhong/673279.html
相关阅读：写作时最容易犯的5个错误