when 是真题里最"多栖"的引导词之一：作关系副词引导定语从句（先行词是时间名词，= at/in which），也作从属连词引导时间状语从句（"当…时"）。两种用法的翻译策略完全不同。
英语六级真题里 when 引导的从句共 902 处实例，覆盖 3 类从句；本页按从句类型分节，精选 37 句真题例句（出自 24 套真题卷，句长 15–49 词）。 每节先给该类型的实例计数与所属从句族入口，再逐句给出例句：高亮从句在原句中的位置，标注它在句中的功能与嵌套层级，附中文翻译、逐句解析与出处试卷； 点句卡末尾的「本句详情」可看结构树逐层拆解、成分与时态标注、考点讲解与真题高频词。
判断要点 看 when 前面：紧跟 time / day / moment 等时间名词多为定语从句；直接修饰主句、可整块移到句首的是时间状语从句。
本页精选的 37 句真题例句已由懒笔记排版为 A4 打印版 PDF，可免费下载，PDF 内的真题出处链接均可点击。
Driver fatigue is thought to be responsible for as many as a fifth of road crashes across the EU, although there are certain times of the day when more accidents happen.
据认为，驾驶员疲劳是欧盟境内多达五分之一道路交通事故的原因之一，尽管一天中的某些时段发生的事故更多。
该从句紧跟先行词 "times of the day"，限定具体是哪一些时段，即“事故发生得更多的时段”。关系副词 "when" 在从句中表示时间状语，相当于 "during which"；没有逗号，属于限制性定语从句。
The convenience of communication—when they need a ride home from school after practice, for instance—often feels like it isn't worth the battle to keep their screen time low and productive, and continue to encourage "real-life" activities outside and with friends and family.
这种沟通上的便利——比如，他们训练结束后需要搭车回家时——常常让人觉得，为了限制他们的屏幕使用时间、确保屏幕时间富有成效，并继续鼓励他们多参加户外活动以及与朋友和家人相处的“现实生活”活动，似乎并不值得费力抗争。
该完整分句位于抽象名词"communication"之后，并由"when"引导；它说明这种交流便利性所对应的具体情境，因而作为对前面名词短语的限制性修饰，而非主句的独立时间状语。"for instance"是其中的插入性举例语。
I believe the moment when computers meet and surpass human intelligence is on the horizon.
我相信计算机达到并超越人类智能的那一刻即将到来。
该从句修饰先行词 "the moment"，说明是哪一个时刻，即“计算机达到并超越人类智能的时刻”。关系副词 "when" 在从句中作时间状语，相当于 "at which time"，从句内部主语为 "computers"，并列谓语为 "meet and surpass"。
This is the mating season of some of the most common varieties, when male house spiders come out of hidden corners to look for females, and garden spiders reach adult size and spin their most dazzling webs.
这是一些最常见种类的交配季节，这时雄家蛛从隐蔽的角落出来寻找雌蛛，并且园蛛长到成年大小并织出它们最耀眼的网。
when引导限制性定语从句,修饰先行词"the mating season"。when在从句中作时间状语,限定了这个交配季节的具体时间范围,即"当雄性家蛛出来、园蛛达到成年体型时"。从句与主句用逗号隔开,但其作用是限定而非补充说明,删除后"the mating season of some of the most common varieties"语义不完整,无法明确是哪个时间段的交配季节。从句内部包含并列结构"male house spiders come out...and garden spiders reach...and spin...",描述交配季节的具体标志。
This is a period when the majority of males once again report a close alliance with same-sex friends.
这是一个大多数男性再次报告与同性朋友有密切联盟的时期。
关系副词"when"引导限制性定语从句修饰先行词"period"，在从句中作时间状语（= in which period）。从句主语"the majority of males"，谓语"report"，宾语"a close alliance"。无逗号隔开，与先行词紧密相连，删去后主句"This is a period"意义残缺（不知是什么样的时期），符合限制性定语从句特征。
And working alone, there have been times when I've found that money alone provides insufficient motivation.
并且独自工作时，有些时候我发现仅仅金钱提供不足够的动力。
关系副词"when"引导限制性定语从句,修饰先行词"times",说明是什么样的时候。when在从句中作时间状语,从句内部结构完整(主语"I"、谓语"have found"、宾语从句"that...")。该定语从句限定了times的具体内容,不可省略。
The year when most Americans began using smartphones was identified as a turning point in young Americans' level of happiness.
大多数美国人开始使用智能手机的那一年被确定为美国年轻人幸福感水平的一个转折点。
关系副词"when"引导限制性定语从句，修饰先行词"The year"，在从句中作时间状语(= in which year)。从句内部结构为"most Americans began using smartphones"，主谓宾完整。无逗号隔开，且删去后主句"The year was identified..."语义残缺(不知道是哪一年),符合限制性定语从句特征。
But surely everyone reading this has had times when you lie in bed for hours, unable to fall asleep because your brain is thinking about work.
但可以肯定的是，每个读到这篇文章的人都曾有过这样的时刻：你在床上躺了几个小时，因为大脑在思考工作而无法入睡。
关系副词"when"引导限制性定语从句修饰先行词"times","when"在从句中作时间状语(= at which times)。从句内部包含"unable to fall asleep"形容词短语作伴随状语,以及"because"引导的原因状语从句。
Middle school is a crucial period when students may become keenly interested in advanced mathematics.
中学是一个关键时期，这时学生可能会对高等数学产生浓厚的兴趣。
"when students may become keenly interested in advanced mathematics" 修饰先行词 "period"，说明这是一个“学生可能对高等数学产生浓厚兴趣的时期”。关系副词 "when" 在从句中作时间状语，相当于 "in which"，从句内部主谓结构为 "students may become"，因此是限制性定语从句。
At a time when young beauty shoppers are often turning to Sephora or Ulta instead of department store beauty counters, Macy's hopes Bluemercury will help strengthen its position in the category.
在年轻美妆购物者常常转向丝芙兰或Ulta而非百货商店美妆柜台的时代，梅西百货希望Bluemercury将有助于加强其在该品类中的地位。
"when"引导限制性定语从句修饰先行词"a time",关系副词"when"在从句中作时间状语(= at which time)。从句主语"young beauty shoppers",谓语"are turning",结构完整。
Whenever you face a situation when you are extremely stressed, try laughing or if not at least smile as it releases chemicals which decrease stress level in the body.
每当你面临一个你极度紧张的情况时，尝试大笑，或者如果不能至少微笑，因为它会释放降低体内压力水平的化学物质。
"when you are extremely stressed" 修饰先行词 "situation"，说明是哪一种 situation；关系副词 "when" 在从句中作时间/情境状语，没有逗号隔开，属于限制性定语从句。
In a time when education is increasingly expensive, public libraries provide information and educational opportunities free for all people, regardless of their socio-economic status.
在教育日益昂贵的时代，公共图书馆为所有人提供免费的信息和教育机会，不论其社会经济地位如何。
"when education is increasingly expensive" 修饰先行词 "time"，说明是什么样的时期；关系副词 "when" 在从句中作时间状语，相当于 "in which"。该从句与先行词之间无逗号，限定 "time" 的含义，因此是限制性定语从句。
We cannot see the moon at times when it is positioned right between the earth and the sun.
我们有时在月球正好位于地球和太阳之间时看不到月球。
关系副词when引导限制性定语从句,修饰先行词times。when在从句中充当时间状语(= at which times),从句主干为"it is positioned right between the earth and the sun"(it指代the moon,is positioned为被动语态谓语,right为副词修饰positioned,between…为介词短语作地点状语)。无逗号隔开、删去后主句"at times"失去具体所指,故为限制性。
They are failing to look ahead at a time when planning for the future is more important than ever.
他们未能展望未来，而在当前这个时候，为未来做规划比以往任何时候都更加重要。
"when" 引导定语从句修饰先行词 "a time",关系副词 "when" 在从句中作时间状语(= at which time),从句内部 "planning for the future" 为动名词短语作主语,"is" 为系动词,"more important than ever" 为比较结构作表语。从句结构完整,符合限制性定语从句特征:紧跟先行词、无逗号隔开、限定 "a time" 的具体所指。
It looks like it—after all, 2012 was the tipping point when more than half of Americans began owning smartphones.
它看起来是这样的——毕竟，2012年是超过一半的美国人开始拥有智能手机的转折点。
关系副词 "when" 引导限制性定语从句,修饰先行词 "the tipping point"。"when" 在从句中作时间状语,指代 "at that point in time"。从句结构完整:主语 "more than half of Americans",谓语 "began owning",宾语 "smartphones"。无逗号隔开,限定性修饰。
At a time when natural history was a valuable tool for discovery, Merian discovered facts about plants and insects that were not previously known.
在自然史是发现的宝贵工具的时代，梅里安发现了关于植物和昆虫的、以前未知的事实。
"when natural history was a valuable tool for discovery" 修饰先行词 "time"，说明“那个时间”具体是什么样的时期；关系副词 "when" 在从句中作时间状语，相当于 "at which time"。该从句限制并具体化 "time"，因此是限制性定语从句。
In the Central Pacific of Costa Rica, the 330-hectare National Wildlife Refuge Baru looks nothing like the cattle ranch it was before 1987, when Jack Ewing decided to turn this large estate into an ecotourism destination.
在哥斯达黎加中太平洋地区，占地330公顷的巴鲁国家野生动物保护区如今已与1987年以前的模样大相径庭。那时，杰克·尤因决定将这片大型地产改造成一处生态旅游目的地。
该从句由逗号与前面的时间名词 "1987" 隔开，补充说明1987年发生的事情。"when" 在从句中作时间状语，先行词是时间名词 "1987"，因此属于修饰名词先行词的非限制性定语从句，而非普通时间状语从句。
Devils Tower is a relic of the past, when the molten rock of the earth's core forced its way to the surface to form the throat of a volcano.
魔鬼塔是过去的遗迹，当时地核的熔融岩石强行到达地表，形成了火山的喉管。
关系副词"when"引导非限制性定语从句,修饰先行词"the past"。从句内部:"the molten rock of the earth's core"作主语,"forced"作谓语,"its way to the surface"作宾语,"to form the throat of a volcano"为不定式短语作目的状语。该从句用逗号与主句隔开,补充说明"过去"具体指哪个地质年代的事件,删去后主句仍完整。
Today's globally networked media and communication system has its origins in the 19th century, when, for the first time, messages were sent electronically across great distances.
当今的全球网络化媒体和通信系统起源于19世纪，当时，首次实现了跨远距离的电子信息传输。
"when"引导的非限制性定语从句,用逗号与先行词"the 19th century"隔开,修饰该时间名词。"when"在从句中作时间状语(= in which),从句主干为被动结构"messages were sent",带方式状语"electronically"和地点状语"across great distances",中间插入强调性状语"for the first time"。该从句补充说明19世纪发生的具体事件,删去后主句仍完整。
Harrogate became a fashionable resort during Victorian times, when people came to take a bath in the mineral waters.
哈罗盖特在维多利亚时代成为一个时尚的度假胜地，当时人们来这里在矿泉水中洗澡。
"when people came to take a bath in the mineral waters" 由关系副词 "when" 引导，前有逗号，补充说明先行词 "Victorian times" 是人们来矿泉水中沐浴的时期；"when" 在从句中作时间状语，不充当主语或宾语，因此是非限制性定语从句。
Travel websites have been around since the 1990s, when Expedia, Travelocity, and other holiday booking sites were launched, allowing travelers to compare flight and hotel prices with the click of a mouse.
旅游网站自20世纪90年代就已经存在，当时Expedia、Travelocity和其他假日预订网站被推出，使得旅行者能够通过点击鼠标来比较航班和酒店价格。
该从句由关系副词 "when" 引导，先行词是表示时间的 "the 1990s"，从句补充说明20世纪90年代发生了什么。它前面有逗号，属于补充说明性质，删去后主句 "Travel websites have been around since the 1990s" 仍然成立，因此是非限制性定语从句。
It was a lazy, hazy, crazy day on the dwarf planet Pluto when New Horizons, a spacecraft from Earth, flew by at a speed of 31,000 mph (miles per hour) two years ago.
两年前，当来自地球的“新视野号”宇宙飞船以每小时 31,000 英里（mph，即英里/小时）的速度飞掠而过时，矮行星冥王星上度过了慵懒、朦胧而疯狂的一天。
该从句由"when"引导，内部有完整主语"New Horizons"和谓语"flew by"，说明主句所说的那一天发生飞掠事件的时间背景，因此是时间状语从句。
When you feel your willpower and motivation fading, remind yourself of those previous experiences and imagine the same happening now.
当你感到自己的意志力和动力正在减退时，提醒自己回想起以往的那些经历，并想象同样的事情正在此刻发生。
该从句由“When”引导，说明主句动作发生的时间背景。“you feel your willpower and motivation fading”内部是完整的主谓结构，其中“your willpower and motivation”是“feel”的宾语，“fading”是宾语补足语。
In the past decade, researchers have shown that when it comes to the duration of making a new behavior a deep-rooted habit there is not a simple answer.
在过去的十年里，研究人员已经表明，当涉及到将新行为培养成根深蒂固的习惯所需的持续时间时，答案并不简单。
时间状语从句，由 "when" 引导，修饰外层宾语从句的 "there is not a simple answer"。"when it comes to" 是固定搭配，表 "当涉及到/谈到"。从句主干是 "it comes to the duration..."，其中 "of making a new behavior a deep-rooted habit" 是介词短语修饰 "duration"。
Vitality comes about when the ties people form with their fellow team members are such that they stay connected even after the team breaks up.
活力的产生是当人们与团队成员形成的联系达到即使团队解散后他们仍然保持联系的程度时。
when引导时间状语从句,修饰主句"Vitality comes about",说明活力产生的时间条件。从句主语为"the ties people form with their fellow team members"(名词+定语从句修饰),系动词are,表语为"such that..."结构,引出结果状语从句。when在此表"当...的时候",符合时间状语从句特征。
The women's movement has been plagued by stereotypes, misrepresentations by the media, and accusations of man-hating and radicalism, when the basic foundation of feminism is simply that women deserve equal rights in all facets of life.
妇女运动一直受到刻板印象、媒体的歪曲报道以及对仇恨男性和激进主义的指控的困扰，而女权主义的基本基础仅仅是妇女在生活的各个方面都应享有平等权利。
when 引导状语从句,此处 when 表让步或对比("然而/尽管"),而非时间;从句主干为 "the basic foundation is that...",that 后引导表语从句。从句内部嵌套了一个表语从句,需递归拆分。
The impact of a basic discovery on human health can be exaggerated so that the public thinks a miraculous cure is a few months to years away when in reality the significance of the study is far more limited.
一项基础发现对人类健康的影响可能被夸大，以至于公众认为一种神奇的疗法距离我们只有几个月到几年的时间，而实际上这项研究的意义要有限得多。
由"when"引导的时间状语从句,但此处when表对比转折含义("然而实际上"),修饰"thinks"的动作,对比公众的想法与现实情况。"in reality"作插入语,从句主干为"the significance of the study is far more limited",采用系表结构,强调现实的局限性。
We need very broad participation to fully address the global tragedy that results when countries fail to take into account the negative impact of their carbon emissions on the rest of the world.
我们需要非常广泛的参与以充分应对全球悲剧，当国家未能考虑到其碳排放对世界其他地区的负面影响时，这种悲剧就会发生。
时间状语从句，由 "when" 引导，修饰定语从句的谓语 "results"，说明悲剧产生的时间条件。从句主语 "countries"，谓语 "fail to take into account"（未能考虑到），宾语为 "the negative impact..."。虽 "when" 通常表时间，但此处更强调"在……情况下/当……时",接近条件意味，但语法归类仍为时间状语从句。
We found that when we taught participants to ask "What if?" and "How can?" questions that nobody present would know the answer to and that would spark exploration, they engaged in better inquiry at the next exhibit—asking more questions, performing more experiments and making better interpretations of their results.
我们发现，当我们教参与者提出“如果怎样？”和“如何能够？”这类在场无人知道答案且会激发探索的问题时，他们在接下来的展览中会进行更好的探究——提出更多问题、进行更多实验并对自己的结果做出更好的解释。
"when" 引导时间状语从句,修饰主句 "they engaged in better inquiry",说明参与者表现出更好探究行为的时间背景。从句内部主干为 "we taught participants to ask questions",其中 "questions" 后带两个并列的限制性定语从句。
The first era began in the nineteenth century and extended into the early twentieth century when it was recognized for the first time that food contained components that were essential for human function and that different foods provided different amounts of these essential agents.
第一个时代开始于19世纪，并延续到20世纪初，当时人们首次认识到食物中含有对人体功能至关重要的成分，且不同食物提供不同数量的这些必需物质。
when引导时间状语从句，修饰主句动作发生的时间点。从句主干为"it was recognized"，it为形式主语，两个并列的that引导的主语从句作真主语，说明被认识到的内容。
Patterns like these begin to form at a small scale when materials undergo processes like drying, freezing, wrinkling, diffusing and reacting.
当材料经历干燥、冻结、起皱、扩散和反应等过程时，类似的纹理会开始在微观尺度上形成。
该完整分句由从属连词 "when" 引导，说明主句所述模式开始形成的时间背景；从句主干为 "materials undergo processes"。
But when it comes to broader questions about "screen time", many professionals as well as parents are confused and uncertain.
然而，一旦涉及“屏幕使用时间”这一更广泛的问题，许多专业人士和家长都感到困惑和不确定。
该从句由"when"引导，主干为"it comes to..."，其中"come to"表示谈到或涉及。它位于主句前，说明主句判断所针对的讨论范围或情境；这里的"when"并非严格表示某一具体时间，更接近“当谈到……时”。
Unfortunately, the opposite is true when the patient is too stubborn and they refuse to listen to us.
遗憾的是，如果患者过于固执，拒绝听取我们的意见，情况恰恰相反。
"when" 引出时间状语从句，修饰主句中的 "is true"，说明“相反的情况成立”的时间或情境；从句内部由 "and" 连接两个并列的有限分句，共同处于 "when" 的管辖范围内。
So when you're constantly on the road and don't own any property or have a fixed address, which city do you call home?
所以，当你一直在外奔波，既没有房产，也没有固定住址时，你会把哪座城市称为自己的家？
“when you're constantly on the road and don't own any property or have a fixed address”由“when”引导，整体作主句的时间状语，说明“which city do you call home?”这一问题所涉及的情境。“you're constantly on the road”与“don't own any property or have a fixed address”构成并列谓语，其中“or have a fixed address”与“don't own”并列，主语“you”省略。
Ewing, now 75, explains this success using the words his friend chose three decades ago: "In Costa Rica, when you stop managing the shrubs, the jungle comes back for its revenge."
如今已75岁的尤因借用朋友三十年前选用的话来解释这一成功：“在哥斯达黎加，一旦你不再管理灌木丛，丛林就会回来复仇。”
该从句由 "when" 引导，说明在停止管理灌木这一情况下丛林会重新回来。这里的 "when" 具有接近“当……时/一旦……”的条件性，不宜仅按单纯时间关系处理，因此归为条件状语从句。
We simply cannot afford to keep our heads buried in the sand when it comes to racial inequity.
当涉及到种族不平等时，我们简直不能把头埋在沙子里。
"when it comes to..."是固定搭配，表示"当谈到/涉及到某事时"，这里"when"引导时间状语从句修饰主句。从句主干是"it comes to racial inequity"，"it"是形式主语，"to racial inequity"是介词短语作状语。
But on what objective basis can you do this when the behaviors they show are so functionally similar to those of other species that have passed the test?
但是，当它们表现出的行为在功能上与其他通过测试的物种的行为如此相似时，你能基于什么客观依据来这样做呢？
when引导时间状语从句(也可理解为条件),修饰主句"can you do this"。从句主干为"the behaviors are similar to those",其中"they show"是定语从句修饰behaviors,"that have passed the test"是定语从句修饰"other species"。从句表达"当/既然行为如此相似时"的时间或条件背景。
英语六级真题中 when 引导的从句共标注出 902 处实例，覆盖 3 类从句：when 引导的限制性定语从句 34 处、when 引导的非限制性定语从句 5 处、when 引导的状语从句 863 处。本页从中精选 37 句真题例句，出自 24 套真题卷，句长 15–49 词（平均 27 词），CEFR 等级构成为 C1 22 句、B2 13 句、B1 1 句、C2 1 句。每句以高亮标出从句在原句中的位置，标注它在句中的功能与嵌套层级，附中文翻译、逐句解析、出处试卷与卷面位置，并可进入单句详情页查看结构树逐层拆解。
关于 when 引导的从句在英语六级真题中的类型分布与判断方法，最常被问到的问题。
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