than可作介词，请看《牛津高阶英汉双解词典》上的解释：

than prep 

used before a n or pron to express a comparison 用於名词或代词前表示比较关系: 

You gave me less than him.你给我的比给他的少（在口语中: 你给我的比他给的少）。

I'm older than her. 我比她年岁大。

Nobody understands the situation better than you. 谁也不如你了解情况。

There was more whisky in it than soda. 那里面的威士忌比苏打水多。