序数词是third，例如：

1. I was pregnant with our third child at the time.当时我正怀着我们的第三个孩子。

2.The third book in the series is currently in preparation.丛书的第三册现在正准备出版。

3.Their horse came third in the race last year.他们的马在去年的比赛中获得了第三名。