Unit 4 语法专项 WordPower 课件(共29张PPT)2025-2026学年译林版英语八年级上册

(共29张PPT)
教学课件
译林英语八年级上册
Unit4 语法专项 +Word Power
祈使句+should&had better提建议+un-/in-/im-反义前缀
全解精讲+分层练习
学习目标
掌握祈使句6种形式的完整用法、结构及使用场景
精准区分should/had better的语气差异，熟练运用提建议句式
掌握un-/in-/im-前缀搭配规则+特殊变化，灵活变反义形容词
能完成填空、句型转换、单选、改错等多样题型，突破高频易错点
能在语境中综合运用本单元语法词汇，提升语言运用能力
语法核心一：祈使句 核心定义+本质特征
祈使句用于发出命令、提出要求、给予建议、发出邀请或表示禁止
主语为第二人称you，因动作指向明确，一律省略不写
核心语法特征：句首直接用动词原形（否定/No型除外）
无时态、人称和数的变化，句式简洁，可通过please调整语气为礼貌型
祈使句六大核心形式总表
类型 完整句型结构 关键细节 例句
肯定祈使句 动词原形 + 其他成分 无附加词，直接动原开头 Put the books on the desk neatly.
Don't型否定祈使句 Don't + 动词原形 + 其他成分 Don't后必接动原，无to Don't draw on the classroom wall.
No型否定祈使句 No + 动名词/名词 表强烈禁止，后接doing/n No smoking. / No photos.
句首礼貌祈使句 Please + 动词原形 + 其他成分 please放句首，后无逗号 Please pass me the English book.
句末礼貌祈使句 动词原形 + 其他成分, please please放句末，前必加逗号 Pass me the English book, please.
建议祈使句 Let's + 动词原形 + 其他成分 Let's=Let us，表一起做 Let's clean our classroom after school.
肯定祈使句 用法细节精讲
适用场景：发出直接的命令、要求、提醒或邀请，语气中性
结构要求：必须以动词原形开头，无任何多余助动词/情态动词
简单例句：Stand up! / Keep quiet! / Wash your hands before meals!
带状语例句：Put the heavy box on the table. / Go to school on time.
单字祈使句：常用动词可单独成句，例：Look! / Listen! / Stop!
Don't型否定祈使句 用法细节精讲
适用场景：劝阻、禁止他人做某事，语气比No型温和，日常使用最多
结构要求：Don't + 动词原形，不可用Not/Doesn't/Didn't替代Don't
核心易错点：Don't后必须接动词原形，绝对不能加to
错误示例：Don't to touch the wet paint
正确示例：Don't touch the wet paint / Don't talk in class / Don't play with fire
No型否定祈使句 用法细节精讲
适用场景：表示强烈、正式的禁止，多用于公共场合、标识牌
结构要求：No + 动名词（doing）/ 名词，后不可接动词原形
接动名词常用示例：No smoking! / No parking! / No running!
接名词示例：No photos! / No food! / No pets!
与Don't型区别：No型更简洁、正式，Don't型更口语、温和
礼貌祈使句 用法细节精讲
核心作用：在命令/要求中加please，让语气委婉、礼貌，避免生硬
句首型结构：Please + 动原 + 其他，无逗号，例：Please open the window!
句末型结构：动原 + 其他 , please，必加逗号，例：Open the window, please!
否定礼貌祈使句：Please + Don't + 动原 + 其他，例：Please don't be late!
易错点：please放句末时，逗号绝对不能省略
建议祈使句（Let's型） 用法细节精讲
适用场景：说话人邀请/提议和听话人一起做某事，包含双方在内
基础结构：Let's + 动词原形 + 其他，Let's是Let us的缩写
否定结构：Let's not + 动词原形 + 其他，不可加to
正确示例：Let's not go out in the heavy rain.
错误示例：Let's not to go out.
句式转换：Let's...的一般疑问句为Shall we... 例：Shall we go shopping
语法核心二：should & had better 提建议 核心共性
两者均为情态类提建议句式，用于给出建议、劝告、提醒或表达责任
后接动词原形，无任何时态、人称和数的变化，所有人称通用
否定形式直接在其后加否定词，无需借助助动词（do/does）
可用于口语和书面语，had better更偏向日常口语，should通用
均可以与祈使句转换，表相同的建议含义
should 用法详解
核心语气：温和、委婉、无强制意味，表应该、应当
核心含义：侧重普通建议、道德责任、义务或轻微劝告
肯定结构：主语 + should + 动词原形 + 其他
建议例句：You should read English for 30 minutes every morning.
责任例句：We should help the old people cross the street.
否定结构：主语 + should not (shouldn't) + 动词原形 + 其他
否定例句：You shouldn't watch TV for too long! / She shouldn't be late for school!
had better 用法详解
核心语气：强烈、直接，带有警告/强调必要性，表最好
核心含义：暗含如果不做，会有不良后果，侧重紧急/必要的建议
肯定结构：主语 + had better ('d better) + 动词原形 + 其他
警告例句：You'd better take an umbrella. It's going to rain.
必要性例句：We had better leave early. The bus will come soon.
否定结构：主语 + had better not + 动词原形 + 其他
易错点：不可说hadn't better，例：You had better not swim in the river.
should & had better 核心对比辨析
对比维度 should had better
语气强度 温和、委婉，无强制 强烈、直接，带警告/后果暗示
否定形式 should not (shouldn't)，可缩写 had better not，不可说hadn't better
缩写形式 无专属缩写 had better = 'd better（口语常用）
核心侧重 普通建议、责任、义务 紧急/必要的建议，警告性劝告
使用场景 正式/非正式均可，书面/口语通用 偏非正式口语，极少用于正式书面
例句对比 You should study hard.（普通学习建议） You'd better study hard.（不努力会考砸）
Word Power 核心：un-/in-/im- 否定前缀 核心定义+作用
三者均为形容词专属否定前缀，加在形容词原级前构成反义词
核心含义：表不、非、无、未，仅改变语义，不改变词性
核心作用：通过前缀快速拓展反义形容词，无需单独记忆新单词
核心规则：不同前缀有固定词根适配性，不可随意混用，部分为特殊变化
un-/in-/im- 前缀 核心搭配规则
前缀 适配词根特征 常用原形容词 变形后反义词
un- 最通用，无字母限制 lucky usual tidy happy unlucky unusual untidy unhappy
in- 多适配c/p/a开头的形容词 correct complete active incorrect incomplete inactive
im- 仅适配p开头的形容词 possible polite perfect impossible impolite imperfect
否定前缀 特殊变化 必背+易错点
able → unable（不可写inable，固定用un-）
patient → impatient（不可写inpatient，inpatient是名词住院病人）
polite → impolite（不可写unpolite，p开头用im-）
important → unimportant（c/p开头但固定用un-）
记忆技巧：特殊变化单独整理，反复区分避免混用
否定前缀 用法细节+语境例句
前缀仅加在形容词前，不可加在动词/名词前
错误示例：unrun / impossible（正确：possible是形容词可加）
变形后仍为形容词，可修饰名词/作表语
修饰名词示例：an unusual gift / an incorrect answer
作表语示例：The gift is unusual. / His answer is incorrect.
语境拓展例句：It's impossible to finish the work in an hour. / Don't be impolite to others.
语法小练1：祈使句填空
用所给词的适当形式完成句子
________ the window, it's cold outside.
______________ play computer games for too long.
______________ me a glass of water.
________ go to the cinema this weekend.
______________ touch the broken glass, it's dangerous.
________ your name on the top of the paper.
Close
Don't play
Please give
Let's
Don't touch
Write
语法小练2：should/had better 填空
根据语境选填should/shouldn't/had better/had better not
You ______________ drink warm water when you have a cold.
We ______________ play in the street, it's very dangerous.
You ______________ hurry up, the bus is going to leave.
She ______________ eat too much sweet food, it's bad for her teeth.
We ______________ listen to the teacher carefully in class.
You ______________ wake up the baby, he is sleeping.
should
had better not
had better
shouldn't
should
had better not
句型转换小练
1. Please open the door.（改为否定句）
________ ________ ________ the door.
2. Let's play football after school.（改为否定句）
Let's ________ ________ football after school.
3. You should go to bed early.（改为同义句，用had better）
You ________ ________ go to bed early
4. You had better not climb the tree.（改为同义句，用should）
You ________ ________ the tree.
5. Be on time.（改为礼貌表达，please放句末）
________ ________ ________, please
6. Don't shout in the library.（改为同义句，用shouldn't）
You ________ ________ in the library.
Please don't open
not play
had better
shouldn't climb
Be on time
shouldn't shout
单项选择小练
1. Who ________ the window, please It's hot.
A. open B. opens C. opening D. to open
2. ________ talk loudly in the hospital.
A. Not B. Don't C. No D. Doesn't
3. Let's ________ a model plane together.
A. make B. making C. to make D. made
4. You ________ finish your homework before playing games.
A. had better B. had better to C. should to D. better
5. It's ________ to finish the work in 5 minutes.
A. possible B. impossible C. polite D. impolite
6. She ________ ask her parents for help if she has problems.
A. should B. shouldn't C. had better not D. better
A
B
A
A
B
A
单项选择小练
1. This room is ________, please clean it!
A. tidy B. untidy C. tidyly D. untidyly
2. You ________ not swim in the deep river, it's dangerous!
A. should B. had better C. had better to D. should to
3. ________ me your new pen, please!
A. Show B. Shows C. Showing D. To show
4. It's ________ to be late for class.
A. polite B. impolite C. possible D. impossible
5. You'd better ________ early to catch the first bus.
A. get up B. gets up C. getting up D. to get up
6. His answer is ________, he needs to check again.
A. correct B. incorrect C. uncorrect D. inpossible
B
B
A
B
A
B
短文填空小练
________ (listen) to the teacher carefully in class. You ________ (should) rush when you do exercises. It's __________ (possible) to get good grades if you are _________ (patient). You ________ (should) ask for help when you have questions. Our classroom is ________ (tidy), let's clean it together. Everyone should be ________ (polite) to others.
Listen
shouldn't
impossible
impatient
should
untidy
polite
短文填空小练
There are many rules in our school. No ________ (run) in the hallway. Please ________ (be) quiet in the library. You __________ (had better) eat in class. You ________ (should) finish your homework on time. It's ________ (usual) to see students late for school. Our teacher often says it's ________ (important) to be honest. Don't be ________ (polite) to your classmates. If you follow these rules, you will have a happy school life.
running
be
had better not
should
unusual
important
impolite
改错题小练
1. Don't to touch the wet paint.
错误：________ 改正：________
2. You should to finish your homework first.
错误：________ 改正：________
3. It's unpolite to talk loudly in the library.
错误：________ 改正：________
4. Let's not to go out in the heavy rain.
错误：________ 改正：________
5. You had better not to eat too much junk food.
错误：________ 改正：________
6. No talk in the reading room.
错误：________ 改正：________
to touch touch
to finish finish
unpolite impolite
to go go
to eat eat
talk talking
单元重点 易混点辨析
祈使句No型后接动名词/名词，Don't型后接动词原形
should语气委婉表建议，had better语气强烈带警告
un-通用，in-多接c/p/a开头形容词，im-仅接p开头形容词
patient的反义词是impatient，不是inpatient
should/had better后接动词原形，不可加to
单元核心 知识梳理
祈使句：六大形式，核心是动词原形开头，No型和Don't型否定形式要区分
提建议：should和had better后接动原，否定形式分别为shouldn't和had better not
构词法：un-/in-/im-加形容词变反义，特殊变化单独记
核心考点：祈使句否定形式、提建议句式语气差异、前缀搭配规则
解题技巧：先判断句式/词性，再根据规则选择正确形式
教学课件
Unit4 语法专项 +Word Power
祈使句+should&had better提建议+un-/in-/im-反义前缀
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