Thirteen 是十三的意思，而thirty則是三十的意思，區(qū)別可以從以下例子看出：

The woman is almost thirty years old, but she has a thirteen years old daughter, she must be married and have child so young. 女人都快三十歲了，卻有一個十三歲的女兒，一定是早結(jié)婚早生子了。