SUFFIX (加在以 4, 5, 6, 7, 8, 9, 10, 11, 12 或 13 结尾的数字后构成序数词表示)“第…” You add -th to numbers written in figures and ending in 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13 in order to form ordinal numbers. These numbers are pronounced as if they were written as words. For example, 7th is pronounced the same as 'seventh', and 5th is pronounced the same as 'fifth'. (加在以 4, 5, 6, 7, 8, 9, 10, 11, 12 或 13 结尾的数字后构成序数词表示)“第…”