1、one，two，three这三个变为序数词分别是first，second，third，这三个需单独记忆。
2、从第四开始，基数词变为序数词都要加th。
3、eight变为序数词的时候少个t不加只加h；nine变为序数词要去掉e再加th。
4、ve结尾的单词five和twelve变为序数词时要把ve改为f，再加th。
5、y结尾的单词即整十数的单词要把y变为ie，再加th。
6、如果把几十几的数变为序数词，只把个位上的数变为序数词就可以。
1到100序数词和基数词（归纳）

BK.Lisa
基数词：1 one 2 two 3 three 4 four 5 five 6 six 7 seven 8 eight 9 nine 10 ten 11 eleven 12 twelve 13 thirteen 14 fourteen 15 fifteen 16 sixteen 17 seventeen 18 eighteen 19 nineteen 20 twenty 21 twenty-one 22 twenty-two 23 twenty-three 24 twenty-four 25 twenty-five 26 twenty-six 27 twenty-seven 28 twenty-eight 29 twenty-nine 30 thirty 31 thirty-one 32 thirty-two 33 thirty-three 34 thirty-four 35 thirty-five 36 thirty-six 37 thirty-seven 38 thirty-eight 39 thirty-nine 40 forty 41 forty-one 42 forty-two 43 forty-three 44 forty-four 45 forty-five 46 forty-six 47 forty-seven 48 forty-eight 49 forty-nine 50 fifty 51 fifty-one 52 fifty-two 53 fifty-three 54 fifty-four 55 fifty-five 56 fifty-six 57 fifty-seven 58 fifty-eight 59 fifty-nine 60 sixty 61 sixty-one 62 sixty-two 63 sixty-three 64 sixty-four 65 sixty-five 66 sixty-six 67 sixty-seven 68 sixty-eight 69 sixty-nine 70 seventy 71 seventy-one 72 seventy-two 73 seventy-three 74 seventy-four 75 seventy-five 76 seventy-
