1 20的英语缩写形式（1-100英语缩写）

应该是1—20的序数词的缩写形式，

1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 11th 12th 13th 14th 15th 16th 17th 18th 19th 20th 。

序数词都表示第几，后跟名词的单数形式。

例如，

my birthday is on January 20th.

this is my thirtieth birthday.