情景导入
学校美术展快到了，小雨的画入选啦！小杰问："When is the art show?"（美术展是什么时候？）小雨看看通知："It's on April 15th."（在四月十五日。）
小杰又神秘地说："My birthday is on April 16th — the day after the show!"（我的生日在四月十六日，就在美术展第二天！）"几号"用英语怎么说？这就要请出序数词：first, second, third……
核心词汇
序数词类：
| 基数词 | 序数词 | 缩写 | 意思 |
|---|---|---|---|
| one | first | 1st | 第一 |
| two | second | 2nd | 第二 |
| three | third | 3rd | 第三 |
| five | fifth | 5th | 第五 |
| nine | ninth | 9th | 第九 |
| twelve | twelfth | 12th | 第十二 |
| twenty | twentieth | 20th | 第二十 |
活动与节日类：
| 短语 | 意思 | 例句 |
|---|---|---|
| art show | 美术展 | The art show is on April 15th. |
| maths test | 数学考试 | The maths test is on May 8th. |
| Children's Day | 儿童节 | Children's Day is on June 1st. |
句型与语法
第一步：序数词怎么变？
- 一般规则：基数词 + th：four → fourth, six → sixth；
- 三个"特殊户"：one → first, two → second, three → third；
- 小变化要注意：five → fifth, nine → ninth（去 e）, twelve → twelfth, twenty → twentieth；几十几只变个位：twenty-first（第二十一）。
第二步：日期怎么说？
- April 15th 读作 April the fifteenth；June 1st 读作 June the first。
第三步：问答日期——注意介词升级为 on！
- When is the art show? — It's on April 15th. （具体到"哪一天"用 on）
- When is your birthday? — It's on October 3rd. （我的生日在十月三日。）
听说训练
活动日期问答（和同伴问答）：
- A: When is the maths test? （数学考试是什么时候？）
- B: It's on May 8th. （在五月八日。）
- A: When is your birthday? （你的生日是什么时候？）
- B: It's on December 21st. What about you? （在十二月二十一日。你呢？）
辨析对比
- in + 月份：in April（只说到月）；on + 具体日期：on April 15th（说到"哪一天"）；
- 基数词说数量：I have three books.（三本书）；序数词说顺序：the third book（第三本书）；听力陷阱：thirteenth（第十三）和 thirtieth（第三十）读音相近，重音不同要听仔细！
文化角
英美日期写法不一样：英国习惯"日在前"（15 April），美国习惯"月在前"（April 15）——课本采用美式。西方孩子过生日会收到写着 Happy Birthday 的贺卡和蛋糕。而在杭州，孩子生日常常还要吃一碗长寿面，寓意健康长长久久。下次给外国朋友写生日贺卡，别忘了把日期写规范哦！
易错点
- 介词混用：The art show is in April 15th. ❌ → The art show is on April 15th. ✅
- 特殊序数词乱加 th：oneth / twoth / threeth ❌ → first / second / third ✅
- fifth 拼错：fiveth ❌ → fifth ✅；几十几全变：twentieth-one ❌ → twenty-first ✅（只变个位数）
考点
- When is + 活动? — It's on + 日期。（必考）；
- 序数词拼写：first / second / third / fifth / ninth / twelfth / twentieth（高频听写词）；
- in 与 on 的选择：in May / on May 2nd（选择题高频）；序数词缩写：1st / 2nd / 3rd / 4th 的对应规则；谈论生日的情景对话：When is your birthday?（口语与听力常考）。
诵读 Read Aloud
Part 1 · 忙碌的四月
April is a busy month at our school. The art show is on April 15th. My painting of the West Lake is in the show. The singing contest is on April 22nd. The sports meet is on April 29th. What a busy and happy month!
Part 2 · 我们的生日
When is your birthday? My birthday is on October 3rd. My mother's birthday is on June 12th. My father's birthday is on December 30th. I will make a card for my mother. Happy birthday, Mum!
诵读小贴士：Part 1 是"介绍活动日期"的标准写话模板（活动 + on + 日期）；朗读时重点练 fifth 和 twentieth 的发音，th 要咬舌尖。