What is the gramatical difference between 光 and 只?
光剩下2毛钱 does not have the same meaning/context as 只剩下2毛钱
It seems there is more emphasis to the part that comes after 光. When is the right time to use one over the other.
Part I - OP Usage
To avoid confusion, Part I will stick to the usage OP is asking, and skip the other meaning of
The following two sentences are the same.
They both can be translated to either of the following.
Only 2 cent left Just 2 cent left
光 mean(or translate to)
just, in this case.
In most cases, following are correct
`只有` = `光有` = `only have` = `just have` `只剩...` = `光剩...` = `only ... left` = `just ... left`
Look at following example, again, all four lines mean the same thing
他只有勇氣,沒有知識 他光有勇氣,沒有知識 He just have courage, don't have knowledge He only have courage, don't have knowledge
However, there are few cases that only one should be use. Look at the following two cases
(1) 快吃吧,只剩一點點 (2) 快吃吧,光剩一點點
For (1), both of the following are correct translations, where the 2nd one is more "English".
Eat faster, only a little is left Finish it, almost done
For (2), it just doesn't sound "Chinese".
(1) 太陽快下山了,只剩一點光 (2) 太陽快下山了,光剩一點光
For (1), translate as follow
Almost sunset, only a bit light is left
For (2), again, it just doesn't sound "Chinese".
(1) 光說不練 (2) 只說不練
Both translate to
Talk only, no action (maybe someone can give a better English way of saying this)
This is a "common phrase". In this case, (1) is the correct way. (2) is acceptable Chinese, but not the usual way for this "combination".
It is difficult to give a generalize rules on when the two are interchangeable and when they are not. The only way to improve is listen more and read more.
PS: Up for more challenge? Add
空 to the group. Have fun and Merry Christmas!
Part II - Learn the Combo
To learn Chinese, you have to learn, or more importantly, memorize the different meaning and usage, when characters are put together in different ways.
I will analogy this to learning spelling of English.
C, etc, most don't have meaning by themselves. When put together in different orders, they means all kinds of things(eg, try put 'h' 'i' 's' 't' in different order).
光說,只說 只剩,光剩 只有,光有
Sometimes they are interchangeable, sometimes not.
光 Light 陽光 Sun light 激光 Laser 月光 Moon light
You can not substitute
只 for the above.
一隻(只)雞 a chicken (Simplified Chinese) 一雙手 a pair of hand 一對手 a pair of hand 兩杯水 two cups of water 一把刀 a knife 一對刀 a pair of knives 一本書 a book
More here. All you can do is memorize them. If you omit them, sometimes it just doesn't sound Chinese, but sometimes the meaning change completely
一把刀 a knife 一刀 a slash / a stab 一對手 a pair of hand 對手 opponent 一手 first hand (car/boat) vs second hand, first owner 一手 stock market, minimum buying quantity (eg. 100shares/order, 500share/order) 一手好車 excellent driving skill 一本書 a book 一書 !@#$, Japanese??
Exception - common phrase, omitting classifier
A chicken die, another chicken start calling
A dead chicken is always replaced by another one.
Describe/conclude being replaced (person, organization, living entity).
Throw your logic away :P
Part III - Bonus - Completely out of Context
月光族 Moon Light Tribe / Tribe of Moonlight
That sounds poetic, romantic, right? The true/current meaning
月 Month(ly) 光 Empty / Use up (money) 族 Type/Group of people
"Direct" translation - People who use up all their money each month.
"English" translation - People living paycheck by paycheck.
It is a common Taiwan usage.
只 is more limited in grammatical scope: it can only function as an adverb, preceding the verb. 光 has a larger range of related uses, from being a pre-verbal adverb (also called a restrictive adverb) like 只, to a resultative complement used when a verb 'finishes' an associated noun (e.g. in 吃光了), as well its adjectival/adverbial meaning of 'empty' and 'naked'. 光 can also precede nouns and other adverbs (e.g. of time) in the sense of "only" where 只 cannot. However, words that include 只 such as 只要、只是 are used in a greater variety of set constructions (among the most well-known being 只要 X 才 Y).
However, both 只 and 光 can be used as pre-verbal (restrictive) adverbs, as the famous "只/光剩下2毛钱" sentence illustrates. There have been various analyses: 光 being more colloquial and characteristic of the spoken language, while 只 is preferred in the standard written language but is itself neutral with respect to spoken vs written. This is perhaps the most basic distinction in their use as adverbs: see Baidu's explanation. It is also known that 只 adopted its meaning of "only" earlier on (at the latest from the late Han dynasty) whilst 光 in this meaning is not even attested in the Kangxi dictionary (see zdic.net).
There is a claim that a clause with 光 implies a negative clause further on. One further explanation found on that website is that 光 with 有 has a focus on things other than the object of 光有, whilst 只有 shifts the focus onto the object of the clause itself. It uses the example 只/光有口号，是没用的 to make this point.
There is also the idea that 只 with quantitative measures (such as in the 2毛钱) means limited to that quantity, whilst 光 focuses on the object and the fact that it is alone. The modified sentence 口袋里只/光剩下2毛钱 illustrates this potential distinction: 只 may allow the possibilities of other non-money items in the pocket, whilst 光 emphasises that this money is all that exists in the pocket.
For some of these later points, there really aren't many trustworthy sources. It may be an interesting point on which to do some further research! There are also a few other words for "only", such as 单 and 仅 which could be examined.
IMO, the difference is quite subtle, but the way I've used them are:
只: "only, just". I think this is more of an objective description of what you have. You can use it to objectively state your situation.
我只有一块钱 = I just have a dollar 我只是不明白你的意思 = It's just that I don't understand what you mean.
光: "only, empty". I think this has a stronger, more expressive meaning of one's situation. I suppose you can use it for emphasis on your situation.
我光有一块钱 = I *only* have a dollar 我把钱花光了= I've spent *all* of my money
I've consulted my cousin who lives and studied in China, here is a summary of his response.
Originally, 光 was used to describe the brightness of flames.
However, it can also be used to describe the barren, emptiness of something (空). If a place is described 明亮透彻无遮挡 (brightness penetrates undeterred), it is the equivalent of saying that it is 无物的开放空间 (an expanse of empty space), allowing the light to penetrate undeterred.
光头 refers to a bald (barren) head. 钱包的钱花光了 refers to 钱包空了 (empty wallet)
只 is a quantifier that is similar in meaning to 独 (single/solitary/independent). It's said that original character depicts a solitary bird on one hand (单手持一只鸟, a pair would be 双手并持一对鸟).
Therefore if you say 口袋里光剩下2毛钱，it implies that 2毛钱 is the only thing you have in your pocket. However, if you say 口袋里只剩下2毛钱，there might be other things inside your pocket besides 2毛钱, such as candy or a phone.
Interesting question: "光" vs "只".
Personally I've said "只剩下2毛钱", but never "光只剩下2毛钱".
There is "guang3 剩下2毛钱" in my dialect (I come form ChangChun, JiLin.). Maybe in other dialects, people uses "光" instead in the place of "guang3".
For the question "When is the right time to use one over the other?"
Use "只" in writen chinese, try to avoid "光" in spoken chinese.
In the sentences you gave, 光 and 只 are very similar and hard to distinguish. But, as you say, they have some differences.
When we say 我只有2元钱了, I imply that the amount of money I have is small, maybe not enough. Like, when you have to pay 10￥, but you only have 2, we say 我只有2元钱.
When we say 我光有2元钱, it implies that apart from these 2￥, we have nothing else.
However, when we want to express that we have nothing except this 2￥, we could either use 光 or 只. But when we want to express that we have a little or not enough money in hand, we may only use 只 in this circumstance.