"All the money in the world " , in this sentence we talk about money in general , right ? I've read a book that says if we're talking about things in general we do not use "the".
So why "the money" ?
Grammar – Why Does ‘Money’ Take ‘The’ in ‘All the Money in the World’?
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Related Solutions
The full-clause form
You are correct: how about can also take a full clause with a subject of its own. A common sort of example is “How about we eat at Sparky’s Diner?” Judging by this graph, this phrasing only started becoming common in print around 1980, and in speech it might be only about 100 years old. The gerund form with an explicit subject (see below) is older and more formal, although that appears to be changing.
In How about subject verb {objects}?, the verb is in the subjunctive mood, but usually people put it in the indicative even though the meaning is subjunctive. Here are two examples in the subjunctive mood:
How about dad pay for the car?
How about dad not pay for the car?
Notice that the negation is done in the usual way for the subjunctive: by putting not in front of the verb, without adding an auxiliary verb. In the indicative mood, these sentences would be:
How about dad pays for the car?
How about dad doesn’t pay for the car?
Here, negation works as usual for the indicative mood.
The gerund form
The gerund form can also take a subject, usually in the possessive case:
How about your taking out the trash?
How about dad’s paying for the car?
This explains the missing “us” you noticed. Made explicit (as is almost never done), that would be:
How about our not talking to her anymore?
Notice that negation works as usual for gerunds (that is, without an auxiliary verb).
The present-participle form
You can also say:
How about dad paying for the car?
How about dad not paying for the car?
How about you taking out the trash?
Notice that negation works as usual for participles (that is, without an auxiliary verb). You can even do this:
How about us not talking to her anymore?
Why all this makes sense
The above all makes sense and doesn’t come across as ungrammatical, even in the rarer forms, because how about x simply raises x for consideration or to get an answer from the listener. The x can be anything: a physical object, a fact, or an unrealized possibility.
“How about this necklace?” asks for the listener’s thoughts about the necklace in regard to whatever the current topic of interest is. Depending on context, the meaning could be equivalent to “How would you like to wear this necklace?” or “How about I wear this necklace?” or “Do you think this is a remarkable necklace?” or even “Admit that this necklace would not have been found in your suitcase if you weren’t cheating on me!”
Raising an unrealized possibility or a fact for comment is really no different than raising an object for comment. The full clause or gerund clause still functions as a noun.
If it’s an unrealized possibility, like “How about you take out the trash?” or “How about taking out the trash?”, then it’s probably a suggestion or proposal.
Subjects are optional on gerunds, so both of these are grammatical: “How about taking out the trash?” and “How about your taking out the trash?”
You can also describe a possibility by naming an object and giving it an imagined adjective such as a present participle, as in: “How about you taking out the trash?” (As a strong hint to take out the trash, this form definitely comes across as informal and disrespectful.)
If it’s an actual fact, like “How about your missing all but two games last season?”, then you can’t use the full-clause form. That would contradict the subjunctive mood inherent in the full-clause form.
I can’t think of any other situations where a full clause can be the object of about. For example, you can’t say “He’s talking about we hire John.” Maybe this is why you haven’t come across it in books or classes about English. (Most likely, books and classes skip it because it’s relatively new.)
The only form that you really can’t use is the infinitive:
How about me pay for the car?
"The money" is a particular source of money
Omnidisciplinarianist's answer starts out by saying (quite rightly) that "the" is used when it is "a specific amount or parcel of money". However, the rest of their answer seems to suggest that the "specific" part is about "being specific to a purpose". I disagree; I would argue that it is about "being specific to a source".
In your example...
Interviewer: "Why do you want this job?"
Girl: "I need the money."
...you rightly observe that the girl hasn't specified what she needs the money for. However, this is not important for her choice of "the money" rather than "money". She means that she needs the money that this job would pay.
Writing this answer has gotten me thinking about this choice of phrase. It occurred to me (and you too may wonder), what's the real difference? A dollar is a dollar, or a pound is a pound. Aside from practical or legal concerns, you would never have reason to say, "I need this money, not that money," if both were the same amount.
While I have said that "the money" is used when referring to a particular source, I think it's worth pointing out that it isn't important for that money to be any different to any other money. If the girl in your example interviewed for two jobs, paying the same, then it's not true that she needs "the money" specific to one job or the other. However, she would still likely say "the money", not because she needs that specific source of money, but because she and the interviewer are talking about a specific source of money already.
In other words, the difference between these phrases...
I need money.
I need the money.
...isn't really that you need this specific source money, but that you are already talking about this specific source of money. There is an implication that this specific source of money is the right amount for you, but that doesn't mean you would change your wording based on whether you had other alternatives available.
Best Answer
This sentence is not talking about money in general. It is talking about a specific set: "all the money in the world", as if it was a specific quantity you could receive:
Other examples talking about a specific set of money:
It is possible to talk about money as a concept, in which case you would not use the definite article. Examples of this:
It is possible to say "all money in the world" to reference the global concept of money, rather than a specific quantity.
[Edit] With regard to FumbleFinger's objection: I would claim "money donated to charities" is either a kind of ellipsis, or else refers to a conceptual subset of the concept of money. In my example, it makes little difference whether I'm talking in general about the practice of donating money, or of a specific instance of some quantity donated. The second half of the sentence applies either way.
I think a more in-depth exploration is out of the scope of the question, as OP asks only what the definite article means in this context, and not whether the definite article is required.