In English, a restrictive clause restricts the scope of the noun or pronoun in front of it (antecedent, head word), while a non-restrictive clause does not. For example,
Restrictive: The New Yorkers who like to walk are healthy.
Non-restrictive: The New Yorkers, who like to walk, are healthy.
In a posting to the Facebook Polyglots group, I'm surprised to find that many non-English-native-speakers have a hard time understanding the difference. I started the discussion because I wanted to see how the sentences are translated to other languages, especially German, where commas are used "profusely". (The two commas in the English sentence are essential in making the distinction between the two types of clauses.) According to the polyglots' responses, it looks like the distinction exists in Romance languages (French, Spanish, Italian, etc.), but not in many others (German, Polish, possibly Russian). In the latter group of languages, breaking up the sentence into two parts is a solution, e.g., "The New Yorkers like to walk and are healthy".
The reason I bring up this topic here is that, when I think of the distinction in Chinese, I find that it too has the difficulty: both sentences would be translated as "爱走路的纽约人身体健康". Does that mean only those New Yorkers who like to walk are healthy (in the restrictive sense), or New Yorkers in general are healthy because they like to walk (in the non-restrictive sense)? If we were to ask the people who understand Chinese and more or less know that New Yorkers walk a lot, I bet most people will interpret it the non-restrictive way: New Yorkers like to walk and they are healthy. But I strongly believe this is context-dependent. By that I mean, if we ask people who understand Chinese and know that Houston is the fattest city in America how to interpret "爱走路的休斯顿人身体健康" (literally "The Houstonians(,) who like to walk(,) are healthy", where the commas are ambiguous as in Chinese), I'm sure most will think in the restrictive sense: Only those Houstonians who like to walk are healthy. It would be unthinkable to say Houstonians in general like to walk, because many start to pant after dragging their unwieldy bodies for one-eighth of a mile. Sadly, fat Houstonians and lean New Yorkers affect the way we read an English sentence.
Lack of distinction between restrictive and non-restrictive clauses in a specific language of course does not mean the grammarians of that language are unaware of it. In case of Chinese, 定语 or attributive word or phrase or clause is said to have both 修饰 (literally "decorative", corresponding to "non-restrictive" here; not "modifying" as some would translate it to) and 限制 ("limiting", "restrictive") functionalities. Nevertheless, most Chinese are not aware of it and subconsciously mix them up, leading to confusion or misinterpretation.
Lastly, I'd like to point out that if English uses an attributive word instead of a clause, the same ambiguity arises. Consider "The hard-working first-generation immigrants deserve our respect". It can mean (restrictive) "The first-generation immigrants that are hard-working deserve our respect", or (non-restrictive) "The first-generation immigrants, who are hard-working, deserve our respect". Since the first-generation immigrants in general are relatively hard-working, the second interpretation may prevail. But if you are of the opinion that a significant proportion of first-generation immigrants are just as lazy as the population in general, the first interpretation sounds better.
