thirteen是序數詞，意思是“第十三”，而thirty是“三十”的意思。因此二者雖然看著比較相似，讀音也相似，但是含義不同。

Thirteen 是十三的意思，而thirty則是三十的意思，區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，一定是早結婚早生子了。

It is half past one.

It is one thirty.

如果為了表示上午或下午，以下午為例：

It is half past one in the afternoon.

It is one thirty p.m.

It is thirteen thirty hours.

It is one-three-three-zero hours.