什么叫做基数词和序数词?

英语上数词分为两大类：基数词和序数词.
基数词是表示数目的词称为基数词,（1）．从1——10 one,two,three,four,five,six,seven,eight,nine,ten． （2）．从 11——19 eleven,twelve, thirteen, fourteen, fifteen, sixteen, seventeen,eighteen, nineteen．
序数词是表顺序的,1）从第一至第十九： one— first two— second/next three— third four-fourth five— fifth six— sixth seven— seventh eight—eighth nine—ninth ten— tenth eleven— eleventh twelve— twelfth thirteen —thirteenth fourteen—fourteenth fifteen—fifteenth sixteen—sixteenth seventeen—seventeenth eighteen—eighteenth nineteen—nineteenth 大多的序数词都是由其相对应的基数词后面添加“th”构成. （2）从第二十至第九十九 整数第几十的形式由其对应的基数词改变结尾字母y为ie,再加“th”构成. twenty——twentieth thirty——thirtieth