QUOTE (Trias1991 @ Dec 27 2010, 02:43 PM)

2. The word "cái" is being used for many things. What is the right use of it?
Cái is one of the main classifiers of Vietnamese language. The usage of cái has been discussed many times but I don't think there's been any conclusive argument for the use of cái because there are "exceptions" everywhere.
In general, "cái" will be used as classifiers for
objects, or
things that do not move (As opposite to "con" which are generally used for things that move like animals).
For example: cái bàn (the table), cái ghế (the chair), cái hộp (the box)...
Exceptions happen when:
1. The shape of the object entitle it to another classifier:
a. cây: classifier for long objects.
- Ex: cây viết (the pen), cây roi, cây quạt
b. viên, ḥn, cục: classifiers for objects that are sphere-like or cube-like. Viên/ḥn are used more by Northern Vietnamese. Cục is used more by Southern Vietnamese.
- Ex: viên đá, ḥn đá, cục đá (stones), viên bi, ḥn bi, cục bi (marbles)
Notes: viên/ḥn/cuc are not always interchangeable. We say "viên ngọc" (gemstone), but we don't say "cục ngọc"
or "ḥn ngọc" [Edit: Actually I think some people so say "ḥn ngọc", but definitely not "cục ngọc"]. We say "viên gạch" or "cục gạch"
but we don't say "ḥn gạch" [On a second thought some people do say ḥn gạch though it's rare], but that's another matter of discussion.
c. lá, tờ, mảnh: classifiers of flat and thin objects
- Ex: lá thư, tờ giấy, mảnh vải...We don't say cái thư, cái giấy, cái vải
d. sợi: classifier for string-like objects
- Ex: sợi chỉ, sợi dây, sợi tóc
e. cuốn, quyển: classifiers for things that are rolled or rollable (thanks pdrive for reminding me of this one)
- Ex: cuốn sách, quyển sách (book), cuốn lịch, quyển lịch (calendar)
Note: You can say either "cuốn lịch" or "tờ lịch" because the calendar is flat when you open it out, but you can always roll it up.
2. When the object goes in pairs, "đôi" or "chiếc" is used as classifier instead.
- Examples: đôi đũa (pair of chopsticks), chiếc đũa (a chopstick), đôi giày (pair of shoes), chiếc giày (a shoe)
Note: you can also say "cây đũa" because the chopsticks are long

Body parts are exceptions. You use "cái" or "con" instead of "chiếc" for body parts
- Examples: đôi tay (a pair of hand), cái tay (hand). You can also say "hai cái tay" (two hands)
- Examples: đôi mắt (a pair of eyes), con mắt (eye). You can also say "hai con mắt" (two eyes).
Notice that we use "con" instead of "cái" for eyes because eyes do move. You can say "well hands and legs also move"...but beat me, I don't know, our ancestors probably had their own way of thinking.
3. Sleeps and dreams have "giấc" as their classifier. Ex: giấc mơ, giấc ngủ, giấc mộng, giấc chiêm bao
4. Sky, earth, moon, cloud, fire, wind, rain, sea...things that represent Mother Nature have no generic classifier. And of course you can't use "cái" for them.
5. You can't use "cái" for plant parts like flower, seeds, fruits. You can use it for "branch" and "root" (though it doesn't sound nice when you do it, if you use "cái" for branch it sounds like putting one classifier on another classifier, which I will discuss later).
6. River, spring...anything related to liquid movement have "ḍng" as their classifier. "Con" can also be used for river and spring (as river and spring move). Ex: ḍng sông (or con sông), ḍng suối (or con suối), ḍng nước, ḍng chảy...
7. Other exceptions:
- Ship, boat go with "con", not "cái".
We say con tàu, con thuyền, con đ̣...not cái tàu, cái thuyền, cái đ̣.
I guess it's because ship and boat do move lol.
The exception is "bè" (raft) which go with cái. We say cái bè, not con bè.
- Chessmen go with con, not cái.
We say con cờ, not cái cờ (cái cờ would be flag, though people would say "cây cờ" or "lá cờ" instead)
I guess chessmen go with con because they move on chess boards lol
- Knife go with con not cái. We say con dao, not cái dao.
I'm not sure why knife, an inanimate object, goes with "con" instead of "cái"
Note: you can also say "cây dao" because knives are long.
8. Classifier in front of another classifier
- Cái classifier has become so generic that it can be put in front of many other classifiers as well
- Ex: cái cây quạt, cái con dao, cái đôi đũa, cái cây đũa, cái chiếc đũa, cái chiếc giầy, cái tờ giấy, cái mảnh vải, cái con mèo, cái con chó, cái con sông, cái con tàu, cái sợi tóc etc.
- If you do that, it won't be grammatically incorrect. However, you should avoid doing that as much as possible because your sentences wouldn't flow nicely if you keep putting one classifier in front of another classifier...unless you want to emphasize something
9. "Cái" can be used to mean "thing"
- Ex: Cái chính (the main thing), cái cần thiết (the necessarily thing)
10. Abstract ideas or Non-tangible things
- Cái can be used as classifier in front of some non-tangible thing. But maybe I shouldn't go into that now since it's gonna make both me and you crazy lol.
P/S: I'm gonna take a break now. I'll type more into this question and the next question tomorrow.