【基数词变序数词顺口溜】在学习英语的过程中，掌握基数词和序数词的转换是一项基础但重要的内容。为了帮助记忆和理解，我们可以借助一些简单的顺口溜来辅助记忆。以下是对“基数词变序数词”规则的总结，并通过表格形式清晰展示。
一、
1. 大多数基数词变为序数词时，只需在词尾加“-th”
例如：four → fourth, five → fifth。
2. 以“-y”结尾的基数词，需将“y”改为“i”，再加“-eth”
例如：twenty → twentieth, thirty → thirtieth。
3. 特殊数字需要特别记忆
如：one → first, two → second, three → third, five → fifth, eight → eighth, nine → ninth, twelve → twelfth。
4. 部分数字有不规则变化
例如：six → sixth, seven → seventh, ten → tenth, fourteen → fourteenth。
5. 使用顺口溜可以帮助快速记忆
比如：“One becomes First, Two becomes Second, Three is Third, and so on...”
二、基数词与序数词对照表
| 基数词（Cardinal） | 序数词（Ordinal） |
| one | first |
| two | second |
| three | third |
| four | fourth |
| five | fifth |
| six | sixth |
| seven | seventh |
| eight | eighth |
| nine | ninth |
| ten | tenth |
| eleven | eleventh |
| twelve | twelfth |
| thirteen | thirteenth |
| fourteen | fourteenth |
| fifteen | fifteenth |
| sixteen | sixteenth |
| seventeen | seventeenth |
| eighteen | eighteenth |
| nineteen | nineteenth |
| twenty | twentieth |
| twenty-one | twenty-first |
| twenty-two | twenty-second |
| thirty | thirtieth |
| forty | fortieth |
| fifty | fiftieth |
| sixty | sixtieth |
| seventy | seventieth |
| eighty | eightieth |
| ninety | ninetieth |
| hundred | hundredth |
三、顺口溜助记法
> One becomes First,
> Two becomes Second,
> Three is Third,
> Four is Fourth,
> Five is Fifth,
> Six is Sixth,
> Seven is Seventh,
> Eight is Eighth,
> Nine is Ninth,
> Ten is Tenth,
> And then it’s all the same: add “-th” to the end.
通过以上总结和表格，可以更清晰地掌握基数词转序数词的规律。同时，配合顺口溜记忆，能有效提高学习效率，减少出错率。
