前两个是一般抽象事物名词，第三个是人的主观感情，前面可以认为省略了my,不能加the!这是我的理解!

加了 冠词<不管是a 还是the>的pity的含义是：可惜，遗憾   It's a pity  he missed the opportunity to travel abroad.
他错过了去国外旅游的机会,真是可惜。But my world isn't your world, more's the pity.
可惜的是，我们是两个世界的人。

The pity of it was that the Americans didn't play cricket.
可惜的是美国人不打板球。

The pity is that it was all completely unnecessary.
遗憾的是这完全没有必要。

The pity of it was that even the least exacting husband should so often desire something more piquant than goodness.
但遗憾的是，即使是最不挑剔的丈夫也时常会渴望一点更为活泼有趣的东西，而不仅仅是善良，

忘了写呗，按道理应该有的，因为都是特指的。