英语中的序数词，完全形式，口语，复数？

twice thin let us either muuuuuuuu come is not classes

fifth

two—— second
fat——thin
let's——let us
too——either
three——third
go——come
isn't-----is not
four（4 基数词~~~）——ourth(只能有序数词了）
class——classes

two: second
fat: thin
let's: let us
too: either, also
mother: mama, mamma, mom, momma
three: third
go: come
isn't: is not
four: 没有同义词
class: classes