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AI 英语语法知识库
时态
Tenses
9
一般现在时
Simple Present Tense
一般将来时
Simple Future Tense
一般过去时
Simple Past Tense
现在完成时
Present Perfect Tense
现在完成进行时
Present Perfect Continuous Tense
过去完成时
Past Perfect Tense
现在进行时
Present Continuous Tense
过去进行时
Past Continuous Tense
将来进行时
Future Continuous Tense
从句
Clauses
7
定语从句
Relative Clauses
名词性从句
Noun Clauses
状语从句
Adverbial Clauses
宾语从句
Object Clauses
主语从句
Subject Clauses
同位语从句
Appositive Clauses
条件状语从句
Conditional Clauses
非谓语动词
Non-finite Verbs
6
动名词
Gerunds
不定式
Infinitives
现在分词
Present Participles
过去分词
Past Participles
非谓语作主语
Non-finite as Subject
非谓语作状语
Non-finite as Adverbial
句子结构
Sentence Structures
4
主谓宾结构
SVO Structure
并列句
Compound Sentences
复合句
Complex Sentences
平行结构
Parallel Structures
学术写作
Academic Writing
5
正式语气
Formal Tone
避免口语化
Avoiding Informal Language
学术句型
Academic Sentence Patterns
段落结构
Paragraph Structure
论证表达
Argumentative Structures
PTE 高频语法
PTE Grammar Patterns
4
Essay 高频句型
Essay Structures
SST 学术句型
SST Academic Structures
WFD 高频结构
WFD Sentence Patterns
Speaking 常用表达
Speaking Structures
句子结构
Sentence Structures
Intermediate to Advanced
复合句
Complex Sentences
复合句（Complex Sentence）是由一个主句（independent clause）和一个或多个从句（dependent clause）构成的句子。从句不能单独成句，必须依附主句表达完整意义。复合句常用于解释原因、表达让步、说明条件、限定名词、补充背景信息或呈现逻辑关系。在PTE Academic和IELTS写作、口语及阅读中，准确使用复合句能够提升句子多样性、逻辑连贯性和语法复杂度，是获得较高语法分数的重要能力。
核心语法结构
Grammar Formula
Independent Clause + Dependent Clause / Dependent Clause + Independent Clause
PTE 高频程度
High
AI 学习推荐
Core Grammar
适用考试
PTE / IELTS
语法结构
Grammar Structure
结构公式
Independent Clause + Dependent Clause / Dependent Clause + Independent Clause
复合句的核心结构是“主句 + 从句”。主句本身意思完整，例如“Students can improve their writing skills”；从句由从属连词（subordinating conjunction）、关系代词（relative pronoun）或疑问词引导，例如“because they receive regular feedback”。当从句放在句首时，通常需要在从句后加逗号；当从句放在句尾时，一般不需要逗号。常见从句包括状语从句（adverbial clause）、定语从句（relative clause）和名词性从句（noun clause）。
Students can improve their writing skills because they receive regular feedback.
学生能够提高写作能力，因为他们会得到定期反馈。
Because online courses are flexible, many adults choose them over traditional classes.
由于在线课程很灵活，许多成年人选择在线课程而不是传统课堂。
The policy that the government introduced last year has reduced traffic congestion.
政府去年推出的政策已经减少了交通拥堵。
It is widely believed that technology has transformed the way people communicate.
人们普遍认为，科技已经改变了人们交流的方式。
使用场景
Usage Scenarios
表达原因与结果
使用because, since, as, so that等引导从句，可以清楚说明事件发生的原因、目的或结果。在学术写作中，这类复合句有助于建立逻辑链条，避免简单句堆砌。
Many students prefer digital textbooks because they are cheaper and easier to update.
许多学生更喜欢电子教材，因为它们更便宜，也更容易更新。
Since public transport has become more reliable, fewer people need to drive to work.
由于公共交通变得更加可靠，较少的人需要开车上班。
表达让步与对比
使用although, even though, while, whereas等引导让步或对比从句，可以体现更成熟的论证能力。IELTS Task 2和PTE Write Essay中常用这类结构呈现平衡观点。
Although social media helps people stay connected, it may also reduce face-to-face interaction.
尽管社交媒体帮助人们保持联系，但它也可能减少面对面交流。
Whereas some people support strict environmental regulations, others worry about their economic impact.
有些人支持严格的环保法规，而另一些人则担心其经济影响。
限定或补充名词信息
使用定语从句（relative clause）可以对名词进行限定或补充说明，使表达更加精确。常见关系词包括who, which, that, whose, where和when。
People who have access to quality education are more likely to find stable employment.
能够接受优质教育的人更有可能找到稳定的工作。
The city, which has invested heavily in public transport, has seen a decline in car use.
这座城市在公共交通上投入巨大，汽车使用量已经下降。
表达条件与假设
使用if, unless, provided that, as long as等引导条件从句，可以表达某一结果发生的前提。PTE和IELTS议论文中经常需要用条件结构讨论政策、教育、科技或环境问题。
If governments invest more in renewable energy, carbon emissions may decrease significantly.
如果政府在可再生能源方面投入更多，碳排放可能会显著下降。
Students can achieve better results as long as they develop effective study habits.
只要学生养成有效的学习习惯，他们就能取得更好的成绩。
表达观点、事实或发现
名词性从句常用于引出观点、研究发现、事实或判断，如that-clause, whether-clause和wh-clause。这类结构在学术英语中非常常见。
Research suggests that regular exercise can improve cognitive performance.
研究表明，规律运动能够提升认知表现。
It remains unclear whether remote work will become the dominant model in the future.
远程办公是否会在未来成为主导模式仍不清楚。
常见错误
Common Mistakes
Incorrect
❌ Because the cost of living is high. Many young people delay marriage.
Correct
✅ Because the cost of living is high, many young people delay marriage.
because引导的是从句，不能单独作为完整句子使用。中文学习者常把原因从句当作独立句。正确做法是把原因从句和主句连接起来；如果从句在句首，从句后通常加逗号。
Incorrect
❌ Although public transport is convenient, but many people still prefer driving.
Correct
✅ Although public transport is convenient, many people still prefer driving.
although已经表示“虽然”，英语中不能再用but连接同一个主句。中文“虽然……但是……”可以成对出现，但英文通常只保留although或but其中一个。
Incorrect
❌ The students which study abroad often become more independent.
Correct
✅ The students who study abroad often become more independent.
当先行词是人时，定语从句通常使用who或that，而不是which。which主要指物或概念。
Incorrect
❌ If governments will reduce pollution, they should invest in clean energy.
Correct
✅ If governments want to reduce pollution, they should invest in clean energy.
条件从句中通常不用will表示将来，常用一般现在时表达将来条件。原句还存在逻辑不清的问题，应表达“如果政府想减少污染”。
Incorrect
❌ The reason why people move to cities is because they can find better jobs.
Correct
✅ The reason why people move to cities is that they can find better jobs.
The reason is that是更规范的学术表达。because在此结构中容易造成重复表达，尤其在正式写作中应避免。
Incorrect
❌ I think that studying overseas which is beneficial for students.
Correct
✅ I think that studying overseas is beneficial for students.
that引导宾语从句后，需要一个完整的从句结构。which不能随意插入句中。中文学习者常误把“这件事”翻译成which，但英语中不需要该关系代词。
Incorrect
❌ People live in rural areas have fewer job opportunities.
Correct
✅ People who live in rural areas have fewer job opportunities.
当一个名词后面直接接一个带谓语的说明部分时，需要使用定语从句引导词。People live in rural areas不能直接修饰people。
Incorrect
❌ When students use AI tools, can improve their efficiency.
Correct
✅ When students use AI tools, they can improve their efficiency.
主句必须有明确主语。中文中可以省略主语，但英语主句通常不能省略。when从句不能充当主句主语。
学术表达
Academic Patterns
Although X may seem beneficial, it can also lead to Y.
尽管X看起来有益，但它也可能导致Y。
Because X has become increasingly common, Y has attracted greater public attention.
由于X变得越来越普遍，Y已经引起了更多公众关注。
It is widely believed that X plays a crucial role in Y.
人们普遍认为，X在Y中发挥着关键作用。
Research indicates that X is closely associated with Y.
研究表明，X与Y密切相关。
If X is implemented effectively, it may contribute to Y.
如果X得到有效实施，它可能有助于Y。
The extent to which X affects Y remains a subject of debate.
X在多大程度上影响Y仍然是一个有争议的话题。
People who lack access to X are more likely to experience Y.
缺乏X的人更有可能经历Y。
This is particularly important because X can influence Y in the long term.
这一点尤其重要，因为X能够长期影响Y。
While X offers several advantages, its limitations should not be ignored.
虽然X具有若干优势，但其局限性不应被忽视。
What policymakers need to consider is whether X can be sustained over time.
政策制定者需要考虑的是，X是否能够长期持续。
PTE 高频应用
PTE Usage
复合句在PTE Academic中使用频率很高，尤其影响Writing和Speaking的Grammar、Written Discourse以及Oral Fluency表现。在Write Essay中，考生需要使用原因从句、让步从句、条件从句和定语从句来展开论证；在Summarize Written Text中，必须用一个语法完整、信息密集的长句概括原文，复合句几乎是必需结构；在Retell Lecture和Describe Image中，适当使用复合句可以展示逻辑关系，但句子不宜过长，以免影响流利度和准确性。
Write Essay
Summarize Written Text
Summarize Spoken Text
Retell Lecture
Describe Image
Read Aloud
Reading: Fill in the Blanks
Reading & Writing: Fill in the Blanks
高频搭配
Common Collocations
play a crucial role in
在……中发挥关键作用
be closely associated with
与……密切相关
contribute to economic growth
促进经济增长
reduce environmental pressure
减轻环境压力
improve academic performance
提升学业表现
have access to quality education
能够获得优质教育
raise public awareness
提高公众意识
address social inequality
解决社会不平等问题
achieve sustainable development
实现可持续发展
pose a significant challenge
构成重大挑战
AI 学习建议
AI Learning Tips
写PTE Write Essay时，每段至少使用一个清晰的复合句，但不要为了复杂而写过长的句子。准确性比长度更重要。
如果从句放在句首，例如Although, Because, If引导的部分，通常在从句结束后加逗号，再写主句。
中文中的“虽然……但是……”翻译成英文时，不要同时使用although和but；二者选择一个即可。
在Summarize Written Text中，可以用定语从句和that从句整合信息，但必须确保整句只有一个完整的句号结尾。
口语中使用复合句时，应优先选择because, although, if, which等高频连接方式，避免因结构过度复杂影响流利度。
AI 练习题
Practice Questions
将两个简单句合并为一个复合句：Many people work from home. Technology has made remote communication easier.
答案：Many people work from home because technology has made remote communication easier. 许多人在家工作，因为科技使远程沟通变得更加容易。
改正错误句子：Although online learning is convenient, but it requires strong self-discipline.
答案：Although online learning is convenient, it requires strong self-discipline. 或 Online learning is convenient, but it requires strong self-discipline. 不能同时使用although和but连接同一个主句。
用who改写句子：Students study regularly often perform better in exams.
答案：Students who study regularly often perform better in exams. 经常学习的学生通常在考试中表现更好。
用if写一个关于环境保护的条件复合句。
答案：If individuals reduce their use of plastic, environmental pollution can be significantly reduced. 如果个人减少塑料使用，环境污染可以显著减少。
将句子改为更学术的复合句：Technology is useful. It may create privacy problems.
答案：Although technology is useful, it may create privacy problems. 尽管科技很有用，但它可能带来隐私问题。
选择正确句子：A. Because the population is increasing. Cities need better infrastructure. B. Because the population is increasing, cities need better infrastructure.
答案：B正确。because从句不能单独成句，必须与主句连接。
用that从句翻译：研究表明，睡眠不足会影响学生的注意力。
答案：Research shows that a lack of sleep can affect students' concentration.
改正错误句子：People which live in large cities often face high housing costs.
答案：People who live in large cities often face high housing costs. 当先行词是people时，应使用who或that，而不是which。