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1、keep doing, keep on doing這兩個詞組均用來表示“不斷做”的意思，但在涵義上有所不同。
keep doing和keep on doing都可表示“不斷（老是）做某事”的意思，強調動作連續不斷，每隔一會兒發生，這時兩者可以換用。不同的是keep doing中的doing是動名詞，作賓語。例如：john always kept (on) asking questions.約翰總是問個不停。news of successes keeps (on) pouring in.捷報頻傳。
keep doing還可表示連續不斷的動作或持續的狀態。keep on doing則沒有這種用法。例如：we kept working in the fields in spite of the rain. 儘管下雨，我們還是堅持在地里幹活。why do the dogs keep barking?這些狗為什麼不停地叫？
2、keep sb. from doing sth., keep sth. from sb.
keep sb. from doing sth.相當於prevent (or: stop) sb. from doing sth., 意為"阻止某人做某事"。
keep sth. from sb.則表示“將某事瞞著某人”的意思。例如：what kept you from joining me? 什麼事情使你不能和我在一起？we must keep them from getting to know our plans.我們必須防止他們知道我們的計畫。it seems that she keeps something from us.她好像有什麼事瞞著我們似的。why did you keep the truth from me? 你為什麼向我隱瞞真相？
3、kind, sort, type這一組詞都表示“種類”，常可互換使用。
kind系普通用語，其含義較模糊，它所指的種類可用任何標準區分，但著重以事物的自然屬性和內在性質為標準來區分。kind常和type換用，但在表示動植物的種類,族及牌類遊戲時，不能用type代替。如：there are different kinds of animals in shanghai wild animal park. 在上海野生動物園有許多不同的動物。computers can actually do many kinds of work. 事實上，電腦能做許多不同的工作。
sort也為普通用語，比kind更口語化，其概念同kind一樣很不嚴密，兩者常可互換，但sort常摻雜說話人的主觀色彩，帶有輕蔑與貶低的含義。如：we talked of all sorts of subjects.我們談了各種話題。these sorts of people are ready to eat anywhere.這種人總是走到哪裡吃到哪裡。
4、know, recognize
know為“認識，熟悉，知道”，表示認識或熟悉某人，某事，某地。它可作及物或不及物動詞，後接名詞，代詞及從句作賓語，另可接含形容詞及不定式的複合結構。如：who knows, perhaps he doesn't care about me at all.誰知道呢，也許他根本不在乎我。have you known oliver long? i knew him as long ago as the year 1984. 你很久以前就認識奧利福了嗎？我在一九八四年的時候就認識他了。i didn't know you were coming today.我不知道你會來。i've never known you so cheerful.我從來不知道你這么開朗。i know her to be a fool.我知道她是個傻瓜。
recognize為“認出，認清，承認”，表示能認出原來認識或曾經見過的人，物及地方，以及承認某事物的客觀存在。它只作及物動詞，後接名詞，代詞及從句作賓語。如：you have grown so tall that i scarcely recognize you.你長成這么高，我幾乎認不出你來了。did you recognize your uncle at once? 你是不是一下子就認出你的叔叔來了？presently i recognized that we were in the atlantic avenue. 現在我知道我們在亞特蘭大大街。
5、keep up, keep up with
keep up既可是動副型短語動詞，也可是動介型短語動詞，主要表示“（鬥志，價格等）不低落”，“維持，繼續”等意。可以用於被動語態。例如：their spirit kept up well in spite of hardships.雖有困難，但他們並不氣餒。prices still keep up.物價仍舊上漲。i hope the weather will keep up.我希望天氣繼續晴朗。they entered into a correspondence which was kept up for almost 10 years. 他們開始通信了，並且把這種通信聯繫保持了十年之久。
keep up with是一個動副介型短語動詞，後須接名詞做其賓語，表示“跟上，與...同步前進”的意思，即有強調並行不悖，不掉隊的意味。只用於主動語態。例如：he walked so fast that i could hardly kept up with him.他走得那么快，我簡直跟不上了。we must keep up with the times. 我們應該跟上時代。
6、knock down, knock out這兩個短語動詞是動副型，knock既可作及物動詞用，也可作不及物動詞用。兩個短語動詞均在句中作謂語，只是意義不同。1. knock down主要表示下列幾種意義：1.擊倒，打倒 2.拍賣給 3.拆卸，拆散 4.（強迫）減價。例如：he was knocked down by a lorry.他被一輛卡車撞倒了。he knocked his opponent down.他將他的對手擊倒。these old houses are to be knocked down.這些舊房子將被拆除。the painting was knocked down to smith for 5 dollars.那幅畫以5美元的價錢賣給史密斯先生了。the machines will be knocked down before being shipped to the persian gulf. 這些機器在運往波斯灣之前將被拆卸。he asked '500 for his car, but i managed to knock him down 10 percent.他的汽車要500美元，但我設法使他減價百分之十。
knock out則主要表示下列幾種意義：1.敲掉，敲空；2.在拳擊中“擊倒”對方，使其在規定時間內不能起立 3.比喻用法：“使……震驚，驚奇”。例如：he knocked the nail out.他把釘子敲了出來。he knocked his pipe out before refilling it.再裝菸絲之前，他磕出了菸斗里的菸灰。joe knocked his opponent out in the first round of the contest. 喬在比賽的第一回合中就把對方擊倒了。 for a moment he was completely knocked out by the news of his friend's death. 他被他朋友逝世的訊息一下子驚得完全呆住。
7、know, know of
know作及物動詞，表示“知道，懂得”的意思時，其後一般接表示事物的名詞，從句，不定式複合結構。但它表示“認識，了解，熟悉”的意思時，其後多接表示人的名詞或代詞，也可接事物名詞。例如：do you know their names? 你知道他們的名字嗎？do you know what his name is? 你知道他叫什麼名字嗎？i never knew him to act without thinking.我從未發現他輕率行事過。i got to know him in the autumn of 1963. 我是在1963年秋天認識他的。
know of亦可解作know about，其後可接表示人或事物的名詞，表示“知道（有），聽說”的意思，指間接地獲得的信息或情況，相當於hear of。例如：how did you come to know of this? 你怎么知道有這事的？i don't know him but i know of him. 我不認識他，但聽說過他。
8、known to, known for, known as這三個形容詞短語在使用中均與聯繫動詞be連用，只是在意義上有所不同。
known to表示“為...所熟知”或“聞名於”等意，值得注意的是，在由及物動詞know的主動句變被動句時，就要用這種結構。例如：the use of gunpowder was known to the chinese before the europeans.中國人懂得套用火藥是在歐洲人之前。luxun is known to the world. 魯迅舉世聞名。
known for和known as的意義和用法與famous for和famous as相同。如：hangzhou is known for the west lake.杭州以西湖而聞名。he is known as a painter. 他以作為一名畫家而出名。