Difference between 必要、需要、应该？

[hoshinoumi]

Basically what the title says, could someone please explain in detail the different uses?? Connotations of when to use one or another and some examples? I use Boya Chinese textsbooks which aren´t exactly very helpful when explaining grammar. This doubt just came up to my mind when  I found this words in different units and realised the book doesn´t compare them at all. The grammar book I use is "Modern Mandarin Chinese Grammar" by Routledge

 

Our teacher gave us an example of 必要:

去旅行要准备很多必要的东西。

So is  必要 an adjective? Can it work as a verb? It is a compulsory obligation (must) or a weak one (should)? Is it formal? informal?

 

 

Here is what I know so far:

应该 is a verb, used in informal or neutral context. It is a moral or social obligation (should)

e.g. 学生应该认真地学习。It means "students should study seriously " but nobody is forcing them, it is something they are advised to do for their own benefit. Am I right with the connotations of 应该?

 

I am clueless about 需要, I don´t have it anywhere in my textbook or exercises, I just came across this word somewhere and would like to know the difference.

 

 

 

 

 

 

Thank you in advance!

[renzhe]

必要 can be used as a noun or an adjective. It describes something that is required. It is very strong because 必 is a strong character.

需要 = need

应该 = should

[hoshinoumi]

So would 必要 be the noun/adj equivalent for the verb 必须??

 

What would be the difference between:

 

学生应该认真地学习。 "Students should study seriously." 

 

学生需要认真地学习。"Students need to study seriously."  This would be a bit more of an "obligation"?? Something like it is the student´s duty?   Compared to yinggai in which they are told what they should?

[fabiothebest]

From what I understood 必要 can be used as a noun (meaning "necessity") or an adjective (meaning "essential", "indispensable", "necessary").

 

需要 can be used as a noun (meaning "need") or as a transitive verb (meaning "to need", or sometimes "to require").

 

应该 can be used as an auxiliary verb (meaning "should", "ought to", "be supposed to" or "had better").

[hoshinoumi]

So:

Subject+需要+Noun --> as in "I need food" Can it also be Subject+需要+another verb+ Noun "I need to buy food?"

 

Subject+应该+ another verb --> as in "I should buy food"

Did I get it right?

[Nathan Mao]

re, #5:  that works for me.

 

To me, when you say 学生需要认真地学习, you are implying that the students have an actual need that can be satisfied by studying.  It would likely be that if they don't study, they won't pass the test, or they won't get into college, or their grades will cause their parents to scold them.

 

To me, when you say 学生应该认真地学习, you are implying there is a choice, and the choice you are stating is preferable.  The range of choices and the reason for the preference is subjective, and that preference could be societal expectations, duty requirements, teacher's request, to comport with students' goals, etc.

 

So to the extent I've considered this over the last few minutes, I think of 需要 as identifying a need, 应该 as identifying a preference between options, and 必要 as identifying something truly essential, indispensable, or non-negotiable (whether noun or verb form).

 

I would use 必须 to identify a compulsion or non-negotiable requirement, so there is some overlap with 必要.  Perhaps 必须 has a slight connotation of external coercion, and 必要 has more of a connotation of internal motivation. 

[陳德聰]

I would use 必须 to identify a compulsion or non-negotiable requirement, so there is some overlap with 必要.  Perhaps 必须 has a slight connotation of external coercion, and 必要 has more of a connotation of internal motivation.

画蛇添足 ! (I disagree completely)

 

必要 just means general necessity, 必要的 is necessary. Of course what is a necessity is subjective, but that doesn't really add any connotation.

 

必须 entails 必要, so it's not some overlap, 必须 always talks about some sort of 必要的事情. If you want to talk about a 必要的东西 you can use 必需. But both of those are outside the scope of OPs question.

[Nathan Mao]

The original poster specifically asked about 必须 versus 必要 in the first line of #3.

If 必须 and 必要的 were exactly the same, one or the other would have disappeared from use, I think.

If something exists in language,MIT exists for a reason.

I'm just trying to tease out the reason both exist by talking it out, although my conclusions (arrived at by repeating a few sentences to myself with both terms and analyzing the subtle differences, if any) certainly could be way off.

[陳德聰]

I didn't say they were the same. 必须 is commonly an adverbial adjunct, whereas 必要 is a noun or an "adjective" as 必要的. If you wanted to tease out differences, you could say that the set of things which are 必要 can be separated into smaller subsets of things which are 必须 and things which are 必需, but they don't have special connotations like the ones you described.

[Summer Song]

In this sentence, 必要 mean necessary. It is an adj. 必 means 必须, 要 means 需要, so together it means 必须要的。

 

需要 just means need. 我需要一支笔, I need a pen. It's a verb.

 

Your understanding about 应该 is perfectly correct！

[Summer Song]

学生应该认真地学习 equals to "Students ought to study seriously."

 

学生需要认真地学习 equals to "Students need to study seriously."

 

You can also feel it in English. What's the difference between those two?

[hoshinoumi]

Wow, got some amazing useful info,  just the kind of in-depht I was looking for. I will try to find as many sentences I can find so I can comprehend what you all guys said. Really good info, thanks

[loganmurphy]

You're right on top of 應該, it's used for something you should do, but ultimately you can choose not to do if you wish(possibly with consequences)

Example:
昨天我們班有大考。很可惜的事是我考得不好。下一次應該努力復習，才會考好。

As for 需要:

It quite simply means you need something, such as in the case of:

我需要多一點錢，才會付得起我想買那一台車子。


必要 is pretty much the same as 需要, though is closer to "must". Example:

你想開車的話，必要去考駕照。

Most importantly, don't over think it, you'll get it through using it a lot! I hope this helps you out!
 

[Yehuda]

Ditto on not over thinking it. And by the way, it often is not very instructive using English grammatical structures to describe Chinese in my experience. This is much more useful when learning a Western language where the structures and grammatical patterns are similar and the languages came from the basically the same places.

 

It can be helpful to get started if you are trying to get the basic usage of new vocabulary, but spending too much time/energy trying to fit Chinese words/phrases/sentences/structures into an English mind 还不如 really trying to just get the basics of the new vocab and forget what you think it means in English while trying to learn it anew in Chinese. I mentioned this in another post, but it works here too. Try as much as possible to learn as you did your first language, naturally. Play with the word, try it out, listen to native speakers use it. You'll own it in very short time!