EN： The past perfect tense ('had' + past participle) is used to show that an action was completed before another action in the past. In this sentence, 'had tested' happened before the past action 'presented'.
中文： 过去完成时（had + 过去分词）用于表示在过去某个动作或时间点之前就已经完成的动作。在本句中，“测试（had tested）”发生在过去的动作“简报（presented）”之前。
By the time the train arrived, we had bought our tickets.
在火车到达之前，我们已经买好票了。
EN： 'By the time' is a subordinating conjunction used to introduce a time clause, meaning 'no later than the moment that'. It is commonly paired with the past perfect tense in the main clause to emphasize completion.
中文： “By the time”是一个从属连词，用来引导时间状语从句，意思是“在……时候之前”或“到……之时”。主句通常会搭配过去完成时，以强调动作的完成。
By the time she finished her homework, everyone had gone to sleep.
在她写完作业之前，大家就已经去睡觉了。
EN： The Past Perfect tense ('had' + past participle) is used to describe an action that was completed before another action or a specific time in the past.
中文： 过去完成时（had + 过去分词）用于描述在过去某个动作或特定时间点之前，就已经完成的动作。
By the time the movie started, we had already bought our popcorn.
在电影开始之前，我们就已经买好爆米花了。
EN： The preposition 'for' is used to indicate a duration of time, showing how long an action has been happening.
中文： 介词“for”用于表示一段持续的时间，说明某个动作进行了多久。
They lived in Paris for three years before moving to London.
在搬到伦敦之前，他们在巴黎住了三年。
EN： In professional and academic settings, referencing the duration of a project (e.g., 'for two months') is a common way to emphasize the effort, dedication, and depth of work put into a task before its presentation or completion.
中文： 在職場或學術情境中，提及專案的持續時間（例如「兩個月」）是常見的表達方式，用以強調在簡報或完工前，團隊對該任務所投入的努力、專注度與工作深度。
EN： The Past Continuous tense ('was coding') is used to describe an ongoing background action in the past, which is often interrupted by a sudden, completed action in the Simple Past tense ('froze').
中文： 过去进行时（was coding）用于描述过去某个正在进行的背景动作，而这个动作通常会被另一个发生在过去、已完成的突发动作（一般过去时 froze）所中断。
While we were watching the movie, the power went out.
我们正在看电影时，停电了。
EN： The subordinating conjunction 'while' is used to introduce a longer background activity. When the 'while' clause comes at the beginning of the sentence, a comma is required to separate it from the main clause.
中文： 从属连词「while」用于引导时间较长的背景活动。当「while」引导的从句置于句首时，必须使用逗号与主句隔开。
While she was cooking dinner, the phone rang.
当她正在做晚饭时，电话响了。
EN： In the tech and software development world, 'coding' is the standard informal term for writing computer programs. The term 'froze' is a common colloquialism used globally to describe a computer screen or application that has become completely unresponsive.
中文： 在科技與軟體開發領域中，「coding」是撰寫電腦程式的標準非正式用語。而「froze」（當機/凍結）是一個全球通用的口語表達，用來形容電腦螢幕或應用程式完全失去響應、無法操作的狀態。
EN： The Past Perfect tense ('had' + past participle) is used to describe an action that was completed before another point in the past. In this sentence, 'had never solved' emphasizes that up until that specific past moment, the experience of solving such a hard problem had not occurred.
中文： 过去完成时（had + 过去分词）用于描述在过去某个时间点或动作之前已经完成的动作或状态。在本句中，“had never solved”强调在过去那个特定时刻之前，从未有过解决如此困难问题的经验。
They had already left when we arrived at the station.
当我们到达车站时，他们已经离开了。
EN： The construction 'such a/an + adjective + singular countable noun' is used to add emphasis, meaning 'of a very high degree' or 'so extreme'.
中文： “such a/an + 形容词 + 单数可数名词”的结构用于加强语气，表示“如此……的……”或“非常……的……”，用来强调程度之深。
It was such a beautiful day that we decided to go for a picnic.
那是如此美好的一天，以至于我们决定去野餐。
EN： The Past Perfect tense ('had' + past participle) is used to show that an action was completed before another action in the past. In this sentence, 'had fixed' happened before 'arrived'.
中文： 过去完成时（had + 过去分词）用于表示在过去某个时间点或另一个过去动作之前，就已经完成的动作。在本句中，「修好程序错误 (had fixed)」发生在「评委抵达 (arrived)」之前。
Before the movie started, we had already bought our popcorn.
在电影开始之前，我们就已经买好爆米花了。
EN： Adverbial clauses of time introduced by 'before' indicate the sequence of events. The event in the 'before' clause (Simple Past) happened after the event in the main clause (Past Perfect).
中文： 由连接词 'before'（在……之前）引导的时间状语从句用来表示事件的先后顺序。'before' 从句中的动作（使用一般过去时）发生在主句动作（使用过去完成时）之后。
Before she went to bed, she had finished her homework.
在她上床睡觉之前，她就已经写完作业了。
EN： In software engineering and tech culture, 'bug' refers to an error or flaw in a computer program. The term historically originates from actual insects causing electrical shorts in early mechanical computers, but today it is standard industry jargon used globally.
中文： 在軟體工程與科技文化中，「bug」指的是電腦程式中的錯誤或缺陷。這個詞的由來歷史悠久，源於早期機械式計算機中真的有昆蟲（bug）飛入導致電路短路，而現今已成為全球通用的標準行業術語。
EN： The Past Perfect tense ('had' + past participle) is used to show that an action happened before another action in the past. In this sentence, 'had forgotten' happened before the main past action 'realized'.
中文： 过去完成时（had + 过去分词）用于表示在过去某个动作或时间点之前就已经发生的动作。在本句中，「忘记保存」（had forgotten）发生的时间点早于主句的过去动作「意识到」（realized）。
She realized she had left her keys at the office.
她意识到她把钥匙忘在办公室了。
EN： The conjunction 'that' is often omitted in informal spoken and written English when introducing a noun clause functioning as the direct object of verbs like 'realize', 'think', or 'know'.
中文： 在口语或非正式书面语中，引导名词性从句作为「realize（意识到）」、「think（认为）」或「know（知道）」等动词之直接宾语的连接词「that」经常会被省略。
I think we made a mistake.
我觉得我们犯了个错误。
EN： The Past Perfect tense ('had' + past participle) is used to describe an action that was completed before another action or a specific time in the past.
中文： 过去完成时（had + 过去分词）用于描述在过去某个动作或特定时间点之前就已经完成的动作。
They had finished the report before the meeting started.
在会议开始之前，他们就已经完成了报告。
EN： The phrase 'many times' acts as an adverbial modifier of frequency, indicating how often the action was repeated in the past.
中文： 短语“many times”（许多次）作为频率副词修饰语，用来表示该动作在过去被重复了多少次。
I have visited that museum many times.
我已经参观过那间博物馆许多次了。
EN： The conjunction 'as' is used to describe two actions happening at the same time, often implying that one event is developing alongside another. It is similar to 'while' or 'when'.
中文： 连接词「as」用于描述两个同时发生的动作，通常暗示一个事件伴随着另一个事件的发展而进行。其用法类似于「while」或「when」。
As the sun set, the temperature dropped quickly.
当太阳下山时，气温迅速下降。
EN： The Past Continuous tense (was/were + verb-ing) is used to describe an action that was in progress at a specific point in the past, emphasizing the duration or the ongoing nature of the activity.
中文： 过去进行时（was/were + 现在分词）用于描述在过去某个特定时间点正在进行的动作，强调该活动的持续性或进行状态。
They were laughing when the movie started.
电影开始时，他们正在大笑。
EN： In technology and startup culture, a 'demo' (demonstration) is a high-stakes moment where creators show their working product to an audience or judges. The phrase 'hearts were racing' is a common idiom used to describe intense anxiety, excitement, or anticipation during such critical moments.
中文： 在科技與創業文化中，「demo」（產品示範）是一個關鍵時刻，創作者必須向觀眾或評審展示實際運作的產品。片語「hearts were racing」（心跳加速）是常用的成語，用來形容在這種關鍵時刻極度緊張、興奮或期待的心情。
EN： The Past Perfect tense ('had' + past participle) is used to show that an action was completed before another action in the past. In this sentence, 'had prepared' happened before 'won'.
中文： 过去完成时（had + 过去分词）用于表示在过去某个动作或时间点之前就已经完成的动作。在本句中，「事前准备」（had prepared）发生在「赢得比赛」（won）之前。
She passed the exam because she had studied hard.
她通过了考试，因为她事前非常努力读书。
EN： The subordinating conjunction 'because' introduces an adverbial clause of cause or reason, explaining why the action in the main clause ('We won') occurred.
中文： 从属连词「because」（因为）引导原因状语从句，用来解释主句动作（We won）发生的原因。
We stayed home because it was raining.
我们待在家里，因为当时正在下雨。
EN： The past perfect tense ('had' + past participle) is used to describe an action that was completed before another action or a specific time in the past.
中文： 过去完成时（had + 过去分词）用于描述在过去某个动作或特定时间点之前，就已经完成的动作或状态。
By the time the movie started, we had already bought our popcorn.
在电影开始之前，我们就已经买好爆米花了。
EN： The verb 'prove' can be used with an object and an object complement (adjective) to show that someone or something is demonstrated to have a certain quality.
中文： 动词 'prove'（证明）后面可接宾语（受词）与宾语补足语（形容词），用来表示某人或某事被证实具有某种特质或状态。
Her dedication proved them wrong.
她的奉献证明了他们是错的。
EN： The Past Perfect tense ('had' + past participle) is used to show that an action was completed before another action in the past. In this sentence, 'had finished' happened before 'felt'.
中文： 过去完成时（had + 过去分词）用于表示在过去某个时间点或另一个过去动作之前已经完成的动作。在本句中，「完成」(had finished) 发生在「感到」(felt) 之前。
After she had left, we started the meeting.
在她离开之后，我们才开始开会。
EN： The verb 'feel' is a linking verb (copula) that is followed by an adjective (proud) rather than an adverb, to describe the subject's state. 'Truly' is an adverb modifying the adjective 'proud'.
中文： 动词「feel」（感觉）是一个连系动词，后面接形容词（proud）而非副词，用来描述主语的状态。而「truly」则是副词，用来修饰形容词「proud」。
They felt extremely happy about the results.
他们对结果感到无比快乐。
EN： The verb 'teach' can take a double object (ditransitive structure) or, as in this case, an indirect object ('us') followed by a noun clause introduced by 'that' acting as the direct object.
中文： 动词「teach」（教导）可以接双宾语结构。在本句中，间接宾语为「us」（我们），而由引导词「that」所引导的名词性从句「that effort pays off」则作为直接宾语。
Experience taught me that patience is a virtue.
经验教会了我，耐心是一种美德。
EN： The phrasal verb 'pay off' is an intransitive idiom meaning to yield good results or succeed after effort has been made.
中文： 短语动词「pay off」在此处作不及物动词使用，为固定短语，意思是“（努力等）得到回报、取得成功”。
All her hard work finally paid off when she passed the exam.
当她通过考试时，她所有的努力终于得到了回报。
EN： The phrase 'effort pays off' reflects a strong cultural value in English-speaking societies (and many others) emphasizing meritocracy and the belief that hard work eventually leads to success. It is a common motivational idiom used in educational and professional settings.
中文： 「effort pays off」（努力終有回報）這句話反映了英語系國家（以及許多其他文化）中強調「功績主義」與「一分耕耘，一分收穫」的價值觀。這是在教育和職場環境中非常常見的勵志用語。
EN： The Past Perfect tense ('had' + past participle) is used to describe an action that was completed before another action or a specific time in the past.
中文： 过去完成时（had + 过去分词）用于描述在过去某个动作或特定时间点之前就已经完成的动作。
By the time the movie started, we had already bought our popcorn.
在电影开始之前，我们就已经买好爆米花了。
EN： The verb 'spend' is followed by a time expression and then a gerund (V-ing) to indicate how time was used to perform an activity.
中文： 动词 'spend'（花费时间）后面接时间表达，再接动名词（V-ing），用来表示花费时间进行某项活动。
She spent two hours studying for the biology exam.
她花了两个小时准备生物考试。
EN： A 'science fair' is a highly common competitive event in American schools where students present science project reports and models. It emphasizes hands-on learning, teamwork, and public speaking skills from a young age.
中文： 「科學展覽」（science fair）是美國學校中非常普遍的競賽活動，學生在活動中展示自己的科學專題報告和模型。這項活動從小就培養學生的動手實作能力、團隊合作精神以及口語表達技巧。
EN： The Past Perfect Tense ('had' + past participle) is used to describe an action that was completed before another action or a specific time in the past.
中文： 过去完成时（had + 过去分词）用于描述在过去某个动作或特定时间点之前，就已经完成的动作。
By the time the teacher arrived, we had finished the experiment.
在老师到达之前，我们就已经完成了实验。
EN： A Relative Clause starting with 'that' is used here as an adjective clause to modify the noun 'model'. Since 'that' acts as the subject of the clause, it cannot be omitted.
中文： 由关系代词 'that' 引导的关系从句（形容词性从句），在此处用来修饰名词 'model'（模型）。因为 'that' 在从句中担任主语，所以不能省略。
They designed a system that saves water.
他们设计了一个能省水的系统。
EN： In modern science fairs and academic competitions, there is a strong emphasis on sustainability and renewable energy ('clean power'). Presenting projects related to solar energy reflects a widespread global educational trend focusing on green technology and environmental awareness.
中文： 在現代的科學展覽與學術競賽中，非常強調永續發展與再生能源（即「乾淨能源」）。展示與太陽能相關的專案，反映了全球教育界對綠色科技與環保意識的高度重視。
EN： The past perfect tense ('had' + past participle) is used to describe an action that was completed before another action in the past. In this sentence, 'had tested' happened before the judges 'came'.
中文： 过去完成时（had + 过去分词）用于描述在过去某个动作或时间点之前就已经完成的动作。在本句中，「测试（had tested）」发生在「评委抵达（came）」之前。
By the time the movie started, we had already bought our popcorn.
在电影开始之前，我们就已经买好爆米花了。
EN： The conjunction phrase 'by the time' means 'no later than the moment that' and is used to establish a time limit or deadline in the past or future. When referring to the past, the clause following 'by the time' uses the simple past tense, while the main clause uses the past perfect tense.
中文： 连接词短语「by the time」意为“在...时候之前”或“到...为止”，用于表示过去或未来某个时间点的截止期限。当描述过去的事情时，紧跟在「by the time」后面的从句使用一般过去时，而主句则使用过去完成时。
By the time Emma arrived at the station, the train had left.
在艾玛到达车站之前，火车就已经开走了。
EN： The Past Perfect tense ('had' + past participle) is used to describe an action that was completed before another action or point in time in the past.
中文： 过去完成时（had + 过去分词）用于描述在过去某个时间点或另一个过去动作之前，就已经完成的动作或状态。
By the time the guests arrived, we had already cleaned the house.
在客人到达之前，我们就把房子打扫干净了。
EN： The verb 'stop' followed by a gerund (verb-ing) means to cease performing an action or activity.
中文： 动词“stop”后面接动名词（V-ing），表示停止正在进行的某个动作或活动。
The baby stopped crying when he saw his mother.
宝宝看到妈妈时就停止哭泣了。
EN： The past continuous tense (was/were + verb-ing) is used to describe an action that was in progress at a specific moment in the past, often interrupted by another shorter action in the simple past tense.
中文： 过去进行时（was/were + 动词-ing）用于描述在过去某个特定时刻正在进行的动作，这个动作通常会被另一个使用一般过去时的较短动作所中断。
While she was reading a book, the phone rang.
当她正在看书时，电话响了。
EN： The subordinating conjunction 'while' is used to introduce a time clause describing a longer background action, typically using a continuous tense.
中文： 从属连词“while”（当……时）用于引导时间状语从句，描述一个较长的背景动作，通常与进行时连用。
While they were playing soccer, it started to rain.
当他们正在踢足球时，开始下雨了。
EN： The past perfect tense ('had' + past participle) is used to describe an action that was completed before another action or point in the past. Here, 'had almost given up' happened before the decision to try again ('decided').
中文： 过去完成时（had + 过去分词）用于描述在过去某个动作或时间点之前就已经完成的动作。在此句中，「几乎快要放弃」（had almost given up）发生在「决定再试一次」（decided）之前。
By the time the teacher arrived, we had already finished the exercise.
在老师到达之前，我们就已经完成了练习。
EN： The phrasal verb 'give up' means to stop trying to do something. When used with 'almost', it indicates that the action of stopping was very close to happening but did not actually occur.
中文： 短语动词「give up」意思是停止尝试、放弃。当与副词「almost」（几乎）连用时，表示放弃这个动作差一点就要发生，但实际上并没有发生。
She never gives up on her dreams, no matter how hard it gets.
无论变得多么困难，她都绝不放弃自己的梦想。
EN： The Past Perfect tense ('had' + past participle) is used to show that an action was completed before another action in the past. In this sentence, 'had fixed' happened before 'glowed'.
中文： 过去完成时（had + 过去分词）用于表示在过去某个动作或时间点之前已经完成的动作。在本句中，「修好（had fixed）」发生在「发光（glowed）」之前。
After we had finished our homework, we went out to play.
在我们写完作业之后，我们就出去玩了。
EN： Adverbial clauses of time introduced by 'after' describe the sequence of events. When the 'after' clause comes first, it is separated from the main clause by a comma.
中文： 由连接词「after（在……之后）」引导的时间状语从句，用来描述事件发生的先后顺序。当 after 引导的从句放在句首时，与主句之间需用逗号隔开。
After she had saved enough money, she bought a new laptop.
在她存够钱之后，她买了一台新笔记本电脑。
EN： The Past Perfect Tense (had + past participle) is used here to describe an experience or state that occurred before a specific point in the past. Combined with 'never', it emphasizes that this was a completely new experience up to that moment.
中文： 过去完成时（had + 过去分词）在此处用于描述在过去某个特定时间点之前所发生或未曾发生的经验。与 'never'（从未）连用，强调直到那一刻为止，这是一个全新的体验。
She had never seen such a beautiful sunset before that trip.
在那次旅行之前，她从未见过如此美丽的日落。
EN： The structure 'so + adjective' is used to emphasize the degree of a feeling or state. 'Relieved' is a participial adjective describing the emotional state of feeling relaxed because something difficult or unpleasant has stopped or not happened.
中文： 「so + 形容词」的结构用于强调某种感觉或状态的程度。'Relieved'（如释重负的、宽心的）是一个分词形容词，用来描述因困难或令人不快的事情停止或未发生而感到轻松的情绪状态。
We were so relieved to hear that everyone was safe.
听到大家平安无事，我们感到非常如释重负。
EN： Adverbial clauses of time introduced by 'when' are used to show that two actions happened at the same time or one immediately after another in the past. In this sentence, both 'watched' and 'worked' are in the simple past tense, indicating simultaneous past actions.
中文： 由连词“when”（当……时）引导的时间状语从句，用来表示两个动作在过去同时发生，或一个动作紧接着另一个动作发生。在此句子中，主句与从句皆使用一般过去时（watched 和 worked），表示过去同时发生的状态或动作。
When the teacher entered the classroom, the students stopped talking.
当老师走进教室时，学生们便停止了交谈。
EN： Adverbs of manner (like 'perfectly') are used to describe how an action is performed. They typically modify verbs and are placed after the verb or the object. Here, 'perfectly' modifies the verb 'worked'.
中文： 方式副词（如“perfectly”）用来修饰动词，表示动作进行的方式或状态。它们通常放在所修饰的动词或宾语之后。在本句中，“perfectly”修饰动词“worked”，表示运作得极为完美。
She plays the piano beautifully.
她钢琴弹得很优美。
EN： In academic and professional settings (such as science fairs, hackathons, or product launches), a 'demo' (demonstration) is a crucial event where creators show their working prototype to judges or clients. The phrase 'everything worked perfectly' carries a sense of immense relief, as live demos are notoriously prone to unexpected technical glitches (often humorously referred to as the 'demo effect').
中文： 在學術或專業場合（如科學展覽、黑客松或產品發表會）中，「demo」（產品演示/實機展示）是一個關鍵環節，創作者必須向評審或客戶展示實際運作的模型。句子中「everything worked perfectly」（一切都運作得非常完美）透露出極大的鬆了一口氣的感覺，因為現場演示極易出現意料之外的技術故障（在科技界常被幽默地稱為「演示效應」或「莫非定律」）。
EN： The Past Perfect tense ('had' + past participle) is used to describe an action that was completed before another action or a specific time in the past.
中文： 过去完成时（had + 过去分词）用于描述在过去某个动作或特定时间点之前，就已经完成的动作。
They had finished the report before the meeting started.
在会议开始之前，他们就已经完成了报告。
EN： The conjunction 'until' is used to show that an activity or situation continues up to a particular time or event. In this sentence, 'felt' is the past simple of 'feel', linking to the adjective 'natural' as a copular (linking) verb.
中文： 连词“until”（直到……为止）用于表示某个活动或状态持续到特定时间或事件。在此句中，“felt”是“feel”的过去式，作为系动词连接形容词“natural”。
We waited in the office until the rain stopped.
我们在办公室里一直等到雨停。
EN： In academic and professional presentations in English-speaking cultures, 'natural' delivery is highly valued. It implies that the speakers have practiced enough to sound conversational and confident, rather than sounding like they are reading from a memorized script.
中文： 在英語系國家的學術與專業簡報文化中，非常看重「自然」（natural）的表達方式。這意味著講者經過充分練習，使說話聽起來像在自然對話且充滿自信，而不是在背誦死板的講稿。
EN： The conjunction 'although' is used to introduce a subordinate clause of concession, showing a contrast. In English, 'although' and 'but' cannot be used in the same sentence to connect two clauses; only one of them is used.
中文： 连接词「although」（虽然）用于引导让步状语从句，表示对比。在英文中，「although」和「but」（但是）不能在同一个句子中同时使用来连接两个从句，只能择一使用。
Although it was raining, we went for a walk.
虽然下着雨，我们还是去散步了。
EN： The past perfect tense ('had' + past participle) is used to show that an action was completed before another action or time in the past. Here, 'had learned' emphasizes the knowledge gained prior to the end of the competition or the moment of reflection.
中文： 过去完成时（had + 过去分词）用于表示在过去某个动作或时间点之前已经完成的动作。在这里，「had learned」强调在比赛结束或反思的那个时刻之前，我们就已经学到了很多东西。
By the time the movie started, we had already bought our popcorn.
在电影开始之前，我们就已经买好爆米花了。
EN： The verb 'show' can take a double object (ditransitive structure): 'show + indirect object (me) + direct object (what...)'. In this sentence, the direct object is a noun clause introduced by the interrogative word 'what'.
中文： 动词「show」可接双宾语（双宾动词结构）：「show + 间接宾语 (me) + 直接宾语 (what...)」。在本句中，直接宾语是由疑问词「what」引导的名词性从句。
She showed me what true friendship means.
她让我明白了真正的友谊意味着什么。
EN： The noun clause 'what patience and teamwork can do' acts as the direct object. Within this clause, 'what' functions as the object of the verb 'do', representing the potential achievements or impact of patience and teamwork.
中文： 名词性从句「what patience and teamwork can do」作为直接宾语。在此从句中，「what」作为动词「do」的宾语，代表耐心与团队合作所能达到的成就或产生的影响。
I want to see what this machine can do.
我想看看这台机器能做什么。
EN： The past simple tense of the verb 'to be' (was/were) is used to ask about states or emotions in the past. In questions, the verb 'were' is placed before the subject 'you'.
中文： 一般过去时的 be 动词（was/were）用于询问过去的状态或情绪。在疑问句中，动词「were」要置于主语「you」之前。
Why were you so late yesterday?
你昨天为什么迟到那么久？
EN： The word 'so' is used as an intensifier before adjectives (like 'nervous') to mean 'to such a great degree' or 'very'.
中文： 「so」在形容词（如「nervous」）前用作修饰语（加强语气），表示“如此地”或“非常”。
She was so happy to hear the news.
她听到这个消息时非常高兴。
EN： In English-speaking cultures, addressing someone directly by their first name (like 'Emma') at the end of a question is a common way to show empathy, direct connection, and personal care, especially when asking about their feelings.
中文： 在英語系國家中，在問句句尾直接稱呼對方的名字（如「艾瑪」）是一種很常見的表達方式，能展現同理心、拉近彼此距離並表達個人關懷，特別是在詢問對方的感受時。
EN： The Past Perfect tense ('had' + past participle) is used to describe an action that was completed before another action or point in time in the past. In this sentence, 'had broken' indicates that the breakdown occurred before the reference point of the story (the next day's presentation).
中文： 过去完成时（had + 过去分词）用于描述在过去某个动作或时间点之前就已经完成的动作。在本句中，「had broken」（已经坏掉）表示故障发生在故事参考点（隔天的简报）之前。
The train had already left when I arrived at the station.
当我到达车站时，火车已经开走了。
EN： Starting a sentence with 'Because' is common in spoken English as a direct, elliptical answer to a 'Why' question, even though it forms a dependent clause (sentence fragment) in formal writing.
中文： 在英语口语中，以「Because」（因为）开头来直接回答「Why」（为什么）的提问是非常常见的省略表达，尽管在正式写作中这会被视为非完整句（从属从句）。
Why did you leave early? Because I was feeling unwell.
你为什么提早离开？因为我身体不太舒服。
EN： In science fairs and academic presentations, technical failures right before the event (often jokingly referred to as 'the demo effect' or 'Murphy's Law') are a common and highly relatable source of anxiety for students and presenters.
中文： 在科學展覽和學術簡報中，活動前夕發生的技術故障（通常被戲稱為「展示效應」或「莫非定律」）是學生和簡報者非常普遍且容易引起共鳴的焦慮來源。
EN： The Past Perfect Tense ('had' + past participle) is used to describe an action that was completed before another action or a specific time in the past.
中文： 过去完成时（had + 过去分词）用于描述在过去某个动作或特定时间点之前，就已经完成的动作。
They had finished the report before the meeting started.
在会议开始之前，他们就已经完成了报告。
EN： The preposition 'before' is used to introduce a point in time or an event that occurs after the action described in the main clause.
中文： 介词「before」（在……之前）用来引出某个时间点或事件，该事件发生在主句所描述的动作之后。
Please wash your hands before dinner.
晚餐前请先洗手。
EN： The phrase 'by the time' is a subordinating conjunction used to introduce a time clause. It indicates that an action was already completed before a specific point in time in the past or future. When referring to the past, the 'by the time' clause uses the Simple Past tense, while the main clause uses the Past Perfect tense (had + past participle).
中文： 「by the time」（到……时候为止）是一个从属连词，用来引导时间状语从句，表示在过去或未来的某个特定时间点之前，另一个动作已经完成。当指过去的事情时，「by the time」从句使用一般过去时，而主句则使用过去完成时（had + 过去分词）。
By the time the movie ended, she had fallen asleep.
到电影结束时，她已经睡着了。
EN： The Past Perfect tense ('had started') is used to emphasize that an action was completed before another action or time in the past. It helps to establish a clear chronological order of events.
中文： 过去完成时（如「had started」）用于强调某个动作在过去的另一个动作或时间点之前就已经完成。这有助于建立事件之间清晰的时间先后顺序。
The train had left when I reached the station.
当我到达车站时，火车已经开走了。
EN： The Past Perfect tense ('had' + past participle) is used to show that an action happened before another action in the past. In this sentence, leaving the notes ('had left') happened before realizing it ('realized').
中文： 过去完成时（had + 过去分词）用于表示某个动作在过去的另一个动作或时间点之前已经完成。在此句子中，「遗忘笔记」（had left）发生在「意识到」（realized）之前。
She realized she had lost her keys.
她意识到她把钥匙弄丢了。
EN： The conjunction 'that' is often omitted in informal English when introducing a noun clause functioning as the direct object of verbs like 'realize', 'think', or 'say'. Here, 'I had left my notes at home' is the object clause.
中文： 在非正式英语中，引导名词性从句作为「realize（意识到）」、「think（认为）」或「say（说）」等动词的直接宾语时，连接词「that」经常会被省略。在此处，「I had left my notes at home」即为宾语从句。
I think we made a mistake.
我想我们犯了一个错误。
EN： The Past Perfect tense ('had' + past participle) is used to describe an action that was completed before another action or a specific time in the past. In this sentence, 'had practiced' happened before the past event 'the show'.
中文： 过去完成时（had + 过去分词）用于描述在过去某个动作或特定时间点之前就已经完成的动作。在本句中，「已经练习」（had practiced）发生在过去的事件「演出」（the show）之前。
They had already eaten dinner before the guests arrived.
在客人到达之前，他们已经吃过晚餐了。
EN： The preposition 'for' is used to indicate a duration of time, showing how long an action lasted. Here, 'for hours' specifies the length of the practicing session.
中文： 介词「for」用于表示一段持续的时间，显示某个动作持续了多久。在这里，「for hours」（好几个小时）明确指出了练习时间的长度。
She studied for three hours last night.
她昨天晚上读书读了三个小时。
EN： The Past Perfect tense ('had + past participle') is used to show that an action was completed before another action in the past. In this sentence, 'had fixed' happened before 'ran'.
中文： 过去完成时（had + 过去分词）用于表示在过去某个时间点或动作之前已经完成的动作。在此句子中，「修好代码 (had fixed)」发生在「运行得好 (ran)」之前。
After she had finished her homework, she went to bed.
在她写完作业之后，她就去睡觉了。
EN： Adverbial clauses of time introduced by 'after' indicate the sequence of events. When the 'after' clause comes first, a comma is used to separate it from the main clause.
中文： 由连接词「after (在...之后)」引导的时间状语从句，用来表示事件发生的先后顺序。当状语从句放在句首时，主句前必须加上逗号隔开。
After we had eaten dinner, we took a walk.
在我们吃完晚餐后，我们去散了步。
EN： The Past Perfect Tense (had + past participle) is used to describe an action that was completed before a specific point in the past. In this sentence, 'had never expected' indicates that the expectation (or lack thereof) occurred prior to the moment the result was revealed.
中文： 过去完成时（had + 过去分词）用于描述在过去某个特定时间点之前已经完成的动作。在本句中，「had never expected」（从未预料到）表示这种“没有预料到”的心态，存在于结果揭晓（过去的某个时刻）之前。
She had never seen such a beautiful sunset before she visited Greece.
在她去希腊旅游之前，她从未见过如此美丽的日落。
EN： The determiner 'such' is used with 'a/an' and a singular countable noun (such + a/an + adjective + noun) to emphasize the degree or quality of something, meaning 'of this kind' or 'so'.
中文： 限定词「such」与「a/an」及单数可数名词连用（such + a/an + 形容词 + 名词），用来强调某事物的程度或特质，意为“如此的”或“这样的”。
It was such a difficult decision that we had to think it over.
那是个如此艰难的决定，以至于我们必须仔细考虑。
EN： In competitive contexts (like sports, elections, or science fairs), 'a close result' or 'a close call' highlights the intense competition where the winner and loser had very little difference in scores or performance. Expressing humility and surprise at a close victory is a common cultural norm in English-speaking academic and professional settings.
中文： 在競爭激烈的環境中（如體育賽事、選舉或科學展覽），「a close result」（勢均力敵的結果）或「a close call」（險勝/千鈞一髮）強調了雙方分數或表現差距極小的激烈競爭。在英語系的學術與專業場合中，對險勝表達謙遜與驚訝是一種常見的社交禮儀。
EN： The Past Perfect Tense (had + past participle) is used to show that an action was completed before another action in the past. In this sentence, 'had not given up' happened before the action of winning ('won').
中文： 过去完成时（had + 过去分词）用于表示在过去某个动作或时间点之前就已经完成的动作。在本句中，“没有放弃（had not given up）”发生在“赢了（won）”这个过去动作之前。
They had already left when we arrived at the station.
当我们到达车站时，他们已经离开了。
EN： The subordinating conjunction 'because' is used to introduce a clause that states the reason for the action in the main clause. Here, it connects the result ('We won') with the cause ('we had not given up').
中文： 从属连词“because（因为）”用于引导表示原因的从句，说明主句动作发生的原因。在此处，它将结果（我们赢了）与原因（我们没有放弃）连接起来。
She stayed home because it was raining heavily.
她待在家里，因为雨下得很大。
EN： In English-speaking cultures, perseverance and 'never giving up' are highly celebrated values, especially in sports, academics, and personal achievements. Expressing success as a result of collective persistence (using 'we') emphasizes teamwork and shared effort over individual talent.
中文： 在英語系國家中，堅持不懈與「永不放棄」是被高度推崇的價值觀，不論是在體育、學術還是個人成就上。將成功歸因於團隊的堅持（使用「we」），更強調了團隊合作與共同努力，而非僅僅是個人才華。
EN： The phrase 'looking back' is a dangling participle used as an introductory adverbial phrase. It is a shortened form of 'when we look back' or 'as I look back', used to set the reflective tone of the sentence.
中文： 「Looking back」（回首过去）是一个分词短语，用作引导性的状语短语。它是「when we look back」或「as I look back」的简化形式，用于奠定句子反思的基调。
Looking back, I realize how much I have grown.
回首过去，我意识到自己成长了多少。
EN： The past perfect tense ('had changed') is used to emphasize that the change occurred and was completed before a specific point in the past, or to highlight the lasting impact of a past event on a subsequent past state.
中文： 过去完成时（had + 过去分词，此处为「had changed」）用于强调该改变发生在过去某个特定时间点之前并已完成，或用以突出过去某事件对随后过去状态的深远影响。
By the time we graduated, that teacher had changed our lives.
在我们毕业之前，那位老师就已经改变了我们的人生。
EN： In English-speaking professional and academic cultures, 'looking back' or self-reflection is highly valued. It is common to conclude a presentation, project, or story by reflecting on personal growth and lessons learned, emphasizing teamwork and transformation over just the final product.
中文： 在英語系國家的職場與學術文化中，「looking back」（回顧/反思）是非常受到重視的環節。在簡報、專案或故事的結尾，人們習慣分享個人成長與學到的教訓，強調團隊合作與心態轉變，而不僅僅是最終的成果。
重要单词附有 IPA 发音、定义、例句和互动式测验。
在本文中： 报告；发表；演示
在本文中： （电脑屏幕）死机；冻结不动
在本文中： 意识到；明白
在本文中： 怀疑；对……表示怀疑
在本文中： 努力；付出
在本文中： 装置；设备；仪器
在本文中： 宽慰的；松了一口气的
在本文中： 耐心；毅力
片语包含类型标示、双语定义、用法说明和例句。
To yield good results; to succeed.
得到回报；取得成功
To stop trying to do something; to surrender.
放弃
To show that someone is incorrect by presenting facts or achieving success.
证明某人是错的
To think about or reflect on something that happened in the past.
回顾；回想