▲所谓现在进行时，其实，本质上是，主系表（或称主补）句型。现在分词不是主语发出的谓语动词，而是形容词表示，主语的一种状态。而系动词 be 也不是助动词。 如 I am eating an apple. 中 eating an apple 是形容词性的，意思是说：我是处在正吃苹果的状态），am 是系动词。——上面这段话，纯属无稽之谈。正确的表述是：“be +现在分词”，构成进行时态。如：She is looking after children. （现在进行时）不可转换说：Looking after children is she.“系表结构”可以是“be +动名词（短语）”：be是系动词，动名词（短语）作表语。如：Her job is looking after children.（主系表）可以转换说：Looking after children is her job.▲你引用的帖子，除了有明显错误外，还把“现在分词”和“动名词”混为一谈。严格来讲，从语法研究的视角看，这是两个截然不同的概念。▲以下是我的原创，内容较多，对这个问题作了详尽的讲解和归纳。请你耐心阅读。
一、动名词和现在分词：两种不同概念的非谓语动词■必修四的语法项目之一是“动词-ing形式”。在附录的语法专题中，是这样论述的：“动词-ing形式由动词原形+-ing形式构成。动词-ing形式能在句中作主语、宾语、表语、定语、宾语补足语和状语，但不能单独做谓语。”之后，列举了一些能作每种成分的例句。显然，课本把动名词和现在分词混为一谈。把动名词和现在分词统称为“动词-ing形式”，表面来看，似乎简化了这两种术语和两个概念，把它们合二为一。但实际上，这是两个不同的事物，有着不同的语法特征和作用。尽管目前有的语法书包括教材在内，开始追逐时髦，更换术语，但是，草莓视频在线观看APP做老师的，并不满足于这种说法。因为从国内外传统的语法观点来看，动名词(Gerund)和现在分词(The Present Participle)，应该有着自己独立的名称和语法特性，这是毋庸置疑的。在第4单元，含有“动词-ing形式”的句子屡屡可见，如：After half an hour of waiting for their flight to come, I saw people enter the waiting area looking around curiously. I stood for a minite watching them and then went to greet them.由此看出，“动词-ing形式”在英语表达中，是十分常见的语言现象。动名词是兼有动词和名词特征的非谓语动词，它是由表示动作的名词发展而来的。现代英语的动名词在古代英语(Old English)中都是表示动作的名词。到了中古英语(Middle English)以后，它的动词性增强了，但同时又保留了原有的名词特征。■动名词由“动词+ing形式”构成，与现在分词同形。动名词几乎具备了名词的全部语法特征，同时又具有动词的某些特征，可以有自己的宾语和状语，有时态和语态变化等。名词可以作句子的主语、宾语（包括及物动词宾语和介词宾语）和表语；名词前可以有名词所有格、物主代词修饰；名词可以作定语。同样，动名词也具备了上述功能。例如：Watching a family of chimps wake up is our first activity of the day. 观看一家黑猩猩梦中醒来是草莓视频在线观看APP那天的第一项活动。Finding a job is difficult these days. 现在找工作不容易。He hasn’t finished reading the science fiction. 他还没读完那部科幻小说。Yuan Longping devotes all his energy to studying rice.袁隆平把他所有的精力献给水稻研究。My favourite sport is playing tennis. 我最喜欢的运动是打网球。His coming made me very happy. 他的到来使我很高兴。We were annoyed by Mary’s crying. 草莓视频在线观看APP对玛丽的哭叫感到恼火。I bought a new writing desk yesterday. 我昨天买了一张新的写字台。■然而，现在分词的语法作用是，跟助动词 be 连用构成进行时态；此外，现在分词的最主要功能是代替状语从句和定语从句，由此简化表达方式，在句中充当各种状语以及定语。例如：1. 构成进行时态：We are having an English lesson now. 草莓视频在线观看APP现在正在上英语课。The telephones is ringing.Would you answer it, please? 电话在响，你能接一下吗？We were discussing the plan the whole morning yesterday. 昨天整个上午草莓视频在线观看APP一直在讨论这个计划。I was writing a letter when you phonesd.你打电话时我正在写一封信。2. 现在分词（短语）作状语：现在分词（短语）作状语。在一个复合句中，当主句的主语跟从句的主语完全一致时，为了表达简练，草莓视频在线观看APP可以把从句转换为分词短语形式，用以代替原来的从句。所以，现在分词（短语）可以表示时间、原因、方式、伴随、条件、结果、让步等。反过来，它又可以转换成相应的状语从句或并列句。(1) 作时间状语：此时相当于when ,while或after等引导的时间状语从句。如:Wandering in the street, she met an old friend of hers. = When she was wandering in the street, she met an old friend of hers.Having finished their work, they had a rest. = After they had finished their work, they had a rest.(2) 作原因状语：此时相当于because, since和as等引导的原因状语从句。如:Not knowing English, he couldn’t understand the film. = Because he didn’t know English, he couldn’t understand the film. Having taught in the school for many years, she knows her workmates very well. = Since she has taught in the school for many years, she knows her workmates very well. (3) 作方式或伴随状语：作方式或伴随状语时，一般不能转化为状语从句，但可以转化成并列句。如:My wife sat in the sofa, reading a magazine. = My wife sat in the sofa and read a magazine.The boy came in, following his father. = The boy followed his father and came in.(4) 作条件状语：此时相当于if等引导的条件状语从句。如:Turning to the right, you will find a hospital. = If you turn to the right, you will find a hospital.Going there by plane, you will arrive this night. = If you go there by plane, you will arrive this night.(5) 作结果状语：此时相当于so that引导的结果状语从句。如:He didn’t pass the exam, making his parents quite disappointed. = He didn’t pass the exam so that it made his parents quite disappointed.(6) 作让步状语：此时相当于though/although，even if等引导的让步状语从句。如:Weighing 50 kilograms, the box was carried away by him. = Though the box weighed 50 kilograms, it was carried away by him.Admitting what he said, I still think that he hasn’t tried his best. = Although I admit what he said, I still think that he hasn’t tried his best.■动名词和现在分词，因为语法书都有专门的讲解，所以有关细节问题
