20的英语序数词怎么写

1. 以数字结尾的序数词

在数字结尾的序数词中，以1、2、3结尾的需要加上相应的后缀，即st、nd、rd，而其他数字结尾则加上th作为后缀。需要注意的是，11、12、13的序数词结尾都是th，不符合上述规则。

例句：

- My birthday is on the 21st of November.

- This is the 32nd edition of the magazine.

- She finished in 3rd place in the race.

- The 10th anniversary celebration was a great success.

- The hotel room is on the 6th floor.

2. 以字母结尾的序数词

以字母结尾的序数词形式比较规范：加-th作为后缀，比如20th、30th、40th等等。

例句：

- The conference will be held on the 25th.

- Today is the 29th of February, a leap year.

- He won the prize for the 50th time.

- The company was founded in the 20th century.

- The event was cancelled on the 60th day of planning.

3. 特殊的序数词

有些序数词比较特殊，需要特别注意。比如，第一到第九十九的序数词都是独立的，不需要任何前缀，直接写出数字和-th后缀就行了。另外，对于100及以上的序数词，需要在百位数字上加上and。

例句：

- There are 60 students in our class.

- He finished the race in 87th place.

- She has lived on this street since the 13th of June.

- The temperature reached 100 degrees Fahrenheit.

- The concert was held on the 201st day of the year.

总结：

- 数字结尾的序数词需要加上相应的后缀，11、12、13的序数词结尾是th；

- 字母结尾的序数词加上-th作为后缀；

- 第一到第九十九的序数词是独立的，100及以上的序数词需要在百位数字上加上and。

例句：

- Today is the 77th anniversary of the liberation of Auschwitz.

- She came in 23rd place in the marathon.

- The 52nd Super Bowl was held in Minneapolis.

- He celebrated his 80th birthday with his family and friends.

- The 101st Airborne Division played an important role in World War II.