such as这个看似非常简单的短语，在用法上却非常有讲究，很多同学都没有搞清楚其背后的逻辑。你是否思考过，such as前面什么时候加逗号，什么时候不加逗号呢？相信这篇文章能给你醍醐灌顶的感觉。
首先需要注意的是，such as一般是对前面的名词进行举例，而不能对动作进行举例。
比如下面这句话就是错误的：It is important to protect the environment, such as dispensing with disposable plastic bags and switching to public means of transport.(X)
在多年的英语教学中，我经常会在学生作文中看到上面这种错误。这属于比较严重的语法错误，写作中会直接导致扣分的。正确的写法：
It is important to lead green lifestyles, such as dispensing with disposable plastic bags and switching to public means of transport.
引领环保的生活方式很重要，比如拒绝使用一次性塑料袋和转而使用公共交通。(对green lifestyles举例)
一、such as前面是否加逗号
such as前面加不加逗号，可以表示不同的逻辑。先来看几句不加逗号的情况：
①Middle managers took charge of functions such as marketing and finance.
中层管理人员负责市场营销和财务等职能。
②Men are usually worse affected, because they dominate sectors such as manufacturing and construction.
男性受(疫情)影响更大，因为他们主导着制造业和建筑业等行业。
③Models such as these should help more students gain qualifications.
诸如这样的模式应该能帮助更多的学生获得学历。
可以看出，在上面几句中，such as...都是对前面的名词起到非常重要的修饰作用，对应的中文为“诸如...的n”“....等n”，如果去掉such as...就会严重影响句意。比如，sectors such as manufacturing and construction就是将范围限制在了传统的实体行业。
因此，当such as...是对前面的名词的具体范围起到限定作用时，such as前面不能加逗号。类似于一个限制性定语从句。
此时的N such as n也可以写成such N as n，表示“诸如n的N”，比如上面几个可以改为：such functions as marketing and finance、such sectors as manufacturing and construction、such models (as these)。
如果such as...所举的例子可有可无，只是起到一个补充性作用，则such as前面可加逗号，也可不加。
比如下面几句：
①The working environment will equip workers with valuable transferrable skills (,) such as commercial awareness, time management and teamwork.
这种工作环境将使工作者具备珍贵的可变通技能，比如商业意识、时间管理和团队合作。
②Left-behind children are likely to develop chronic mental health problems (,) such as anxiety, low self-esteem and depression.
留守儿童可能会出现慢性心理健康问题，如焦虑、自卑和抑郁。
但是，如果出现下面这种情况，则such as前面逗号必不可少：当such as...与被修饰的名词中心词之间隔了其他成分，比如后置定语或谓语，则such as前面需要加上逗号。比如：
①Industries involving face-to-face interaction, such as hospitality, have suffered most.
涉及面对面交涉的行业，比如餐饮服务业，遭受了最大的打击。
②The pattern is particularly marked in countries that rely heavily on apprenticeships, such as Denmark, Germany and Switzerland.
这种模式在严重依赖学徒制的国家尤为显著，比如丹麦、德国和瑞士。
③Higher-quality evidence is also needed, such as large-scale trials using established protocols.【被举例的名词可以是不可数名词或可数名词单数】
那么，当被举例的名词后面接了一个较长的定语从句，但是又想让例子先被读者读到时，就可以将例子成分提前到被举例的名词后面作插入语，这样也可以使句子更加平衡：
①Facial expression is but one of a number of non-verbal cues, such as body posture, that people use to communicate with each other.
面部表情只是人们用来交流的许多非语言信号(比如身体姿势)之一。
②Intensive, hands-on programmes help children develop important habits, such as conscientiousness, which do not show up on tests but are clearly useful later in life.
密集的动手课程有助于孩子们养成那些考试不考但今后生活中明显有用的重要习惯，比如认真。
上面讲的规则和用法也基本适用于like/including。
二、such as后面接什么成分
such as后面除了接大家比较熟悉的名词和动名词之外，还有一种常见用法是接介词结构。该介词结构经常是与前面被举例的名词构成逻辑上的连接。此时such as前面通常加逗号。比如：
①Other jobs, such as in chemical factories or ship-breaking yards, are viewed as even more hazardous.
其他的工作，比如化工厂和造船厂的工作，被视为甚至更危险。
②Utility networks, such as for electricity, gas, water, and sewage, work the same way.
公共设施网络，如电力、天然气、水和污水网络，运作的方式相同。
③There are also helpful advice, such as on how to better manage your credit cards.
也有一些有益的建议，比如关于如何更好地管理信用卡的建议。
可以理解为介词前面省略了与被举例名词相同的词，从而避免重复。比如第①句就相当于：
Other jobs, such as jobs in chemical factories or ship-breaking yards, are viewed as even more hazardous.
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