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。