序数词firstsecondthirdfourthfifthsixthseventheighthninthtentheleventhtwevlfththirteenthfourteenthfifteenthsixteenthseventeentheighteenthnineteenthtwentiethtwenty-firsttwenty-secondtwenty-thirdtwenty-fourthtwenty-fifthtwenty-sixthtwenty-seventhtwenty-eighthtwenty-ninthtirtieth基数词：1one2two3three4four5five6six7seven8eight9nine10ten11eleven12twelve13thirteen14fourteen15fifteen16sixteen17seventeen18eighteen19nineteen20twenty21twenty-one22twenty-two23twenty-three24twenty-four25twenty-five26twenty-six27twenty-seven28twenty-eight29twenty-nine30thirty