join
［误］ did you attend the football club?
［正］ did you join the football club?
［析］ join经常用于参加某个团体、政党，并作为其中的一个成员；attend则重点强调出会议、到场，而不一定进行具体活动，如： did you attend the meeting yesterday?而take part in则强调参与某些具体活动或运动，如： i take part in the football game.
just
［误］ i have finished my work just now.
［正］ i finished my work just now.
［析］ just now意义"刚才"，所以句中的谓语动词要用过去式。
［误］ just i won the game.
［正］ i just won the game.
［析］ just单独使用时不应放在句首，而应放于① be动词之后，如： he is just a student.② 名词与一般动词之间。③ 用在第一助动词之后，如： i have just returned home. 但just与其他词组成词组时，如just now, just then, 则可用于句首和句尾。如： just then he saw the bus coming.
just justly
just常用于三种含意： ① 恰好，如： it's just five o'clock. ② 仅仅，相当于only, 如： i have just enough money to buy a dictionary. ③ 不久前，如： i just missed my old friend; he left a few minutes ago. 而justly其意为"公正的"，如： he was justly punished for his crimes.
k
keep
［误］ she was keeping something to her father.
［正］ she was keeping something from her father.
［析］ "对某人隐瞒某事"要用"keep something from somebody"句型。
［误］ he kept to repeat the word again and again.
［正］ he kept repeating the word again and again.
［析］ keep doing something为连续不断地做某事。有时可以与keep on doing something互换。它们的区别在于keep doing something意为该动作一直不停地在进行中，如： when the train started, she kept waving her hand. 而keep on doing something则表示该动作可能停停顿顿但却一直在进行中，如： he kept on making the same mistakes in grammar.
［误］ we must keep up the times.
［正］ we must keep up with the times.
［析］ 这句话意为"我们必须赶上时代"，keep up with是"赶上"之意，而keep up则是"坚持下去"的意思，如： keep it up, don't stop now!
key
［误］ i lost the key of the door.
［正］ i lost the key to the door.
［析］ 英语中讲某某的东西一般要用of，而key, entrance, answer则多用to，如："门的钥匙"为key to the door, "高速公路入口"为entrance to the highway, "问题的答案"为the answer (key) to the question.
kind
［误］ this kind of books are not good.
［正］ this kind of books is not good.
［析］ kind在这种句式中应作为主语，如果讲those kinds of books are very good. 则是正确的。
kind sort type
kind和sort为同义词，意为"种类"，而type则为"型号"，如： what type of this car do you want?(你想要这种车的什么型号?)
knock
［误］ someone was knocking the door.