英语序数词1-20是 :

firstsecond thirdfourth fifth

sixth seventh eighth ninthtenth

eleventhtwelfth thirteenthfourteenthfifteenth

sixteenthseventeentheighteenth nineteenth twentieth

1~20英语序数词

first,second ,third,fourth,fifth,sixth,seventh,eighth,ninth,tenth,eleventh,twelth,thirteen,fourteenth,fifteenth,sixteenth,seventeenth,eighteenth,nineteenth,twentieth。