一到二十的基数词：
one
two
three
four
five
six
seven
eight
nine
ten
eleven
twelve
thirteen
fourteen
fifteen
sixteen
seventeen
eighteen
nineteen
twenty
一到二十的序数词：
first
second
third
fourth
fifth
sixth
seventh
eighth
ninth
tenth
eleventh
twelfth
thirteenth
fourteenth
fifteenth
sixteenth
seventeenth
eighteenth
nineteenth
twentieth
