该 - How do you know when to use it? Nothing to do with 应该

Question

In the sentence below, why do you need 该公司? Chinese is contextual, right? 公司 talked about previously is 苹果. Instead of 该公司, why not use 它? Or 这个公司?

也有一些分析师和投资者为苹果辩护，他们说，该公司 完全清楚自己在做什么，设定的价格也符合 该公司 的策略。

But there were some analysts and investors who came to the company’s defense and said that Apple knew exactly what it was doing, and set the price accordingly. (NYT translation)

http://cn.nytimes.com/technology/20130912/c12iphone/dual/

Here's another example:

路易斯安那州共和党众议员约翰·弗莱明(John Fleming)说，“奥巴马医改法案(Obamacare)是国会有史以来通过的最危险的立法案。”他还说，该法案 是“自大萧条(Great Depression)以来”，美国所面临的“最根本的经济威胁，所以，我认为，多一点额外的赤字不算什么。”

“Obamacare is the most dangerous piece of legislation ever passed in Congress,” said Representative John Fleming, Republican of Louisiana. “It is the most existential threat to our economy” that the country has seen “since the Great Depression, so I think a little bit of additional deficit is nothing,” he added.

http://cn.nytimes.com/world/20130913/c13fiscal/dual/

Answer 1

该 is the formal equivalent of the word aforementioned or said:

该公司 - the said company
该法案 - the aforementioned legislation

It is usually found in text to refer back to something that was mentioned previously.

Informally, you can also use 那. Here is the meaning from 汉典:

那，著重指出前面說過的人或事物：～地。～書。

Answer 2

In this situation, 该 is just a more formal way of 这个. Both of them mean "this".

这个 is typically consider too casual to this context.

You can use 此 or 该 instead of 这个 in this kind of context.

Answer 3

In this case, I think "该" is just a formal language meaning "the" (that has been mentioned) or "this".

Answer 4

”该“ can be a rude word too. It means deserve.

For example.

小红说，小明鼻子被小刚打破了， 小刚还说“该！”。

该 is a modal particle, it emphasise 小刚‘s mind about 小明’s nose, "you deserve it!".

In both of OP's examples, "该" has a sense of negative feeling about the object it represents, so that "该" has the function of emphasis on the meaning of 'the', or 'this'. If you are writing something in a positive manner, avoid use "该".