序数词:
first
second
third
fourth
fifth
sixth
seventh
eighth
ninth
tenth
eleventh
twelfth
1st
2nd
3rd
4th
5th
6th
7th
8th
9th
10th
11th
12th
thirteenth
fourteenth
fifteenth
sixteenth
seventeenth
eighteenth
nineteenth
twentieth
twenty-first
twenty-second
twenty-third
thirtieth
13th
14th
15th
16th
17th
18th
19th
20th
21st
22nd
23rd
30th
还有31到50.