My question is as the title. The sentence "school bus is coming" is translated as "校车来了". I understand this translation because "了" here indicates a new situation. But why are "校车来着" or "校车正来" WRONG?
[Edited to discuss 正, 在, and 著]
There is a discussion of 在 and 著 in Li and Thompson's 1981 book Mandarin Chinese: A Functional Reference Grammar. They don't have much to say about 正. My own feeling is that this is usually used with either 在 and 著; it seldom, if ever, appears by itself. Sentences such as 他正吃飯 are simply odd. I am not a native speaker, so I'm ready to be corrected on this.
Both 在 and 著 are durative markers, but they still differ in meaning. L&T's examples of the difference include:
他在穿皮鞋: He is putting on leather shoes
他穿著皮鞋: He is wearing leather shoes
Their explanation for the difference here is that 在 is used with persistent actions (actions that have some duration), while 著 is used with actions that result in a persistent state. 穿 can have either of these interpretations, so both sentences are good, but each has a different meaning. Again, I think 他正穿皮鞋 is just odd here, better to say 他正在穿皮鞋, or 他正穿著皮鞋. In neither case does this actually change the meaning, it simply emphasizes the durative nature of the action or result.
In the case of 來, I think the Chinese logic is that "come" is not a persistent action. Instead, it is what Quirk et al (1981) call a transitional action. Other examples they give are:
The train is arriving at the station
It looks like he is scoring a goal
According to Quirk, transitional actions do not have a durative meaning, and so for these cases English progressive has an anticipatory meaning, i.e. a period leading up to the transition. For these cases, Chinese doesn't use either 著 or 在 (since there is no persistent action or state). Instead it uses forms such as 快...了:
She is dying 她快死了.
She is coming 她快來了.
Since these are not durative sentences, many languages do not use progressive forms here. In this case it is English that is exceptional, rather than Chinese.
As @Stan said in the comment, the issue is with the notion of "arrive". If the bus is in sight and will stop in short time, then in Chinese "it has arrived".
车来了 meaning either bus is going to arrive in short time, or it has arrived
车已经来了 (more often 车已经到了) meaning bus has arrived
车正在来 meaning bus is on its way -- will take a while
校车来了 could mean "the school bus" is coming, but notice that it can also mean "the school bus has come";
来着 is usually used with "what" and is usually used in northern Chinese Mandarin dialect. In this context, it is wrong;
正来 is correct, or rather, not wrong. The problem is, it does not sound like a very common oral expression.
来 is frequently used to cooccur with the bound reading in the immediate situation. For example, we can say 来了. By contrast, 着 cannot do the same but indicates duration, for instance, *来着 sounds bad. Crucially, the action implied by 来 need to refer to the speaker, but 着 does not seem to do that, for example, 说着他走了.
First of all:
- "校车来了" means "the school bus has arrived"
- while "校车来着" and "校车正来" mean "the school bus is arriving"
- The more grammatically correct way of saying "校车来着" and "校车正来" would be "校车在来着" and "校车正在来", the "在" acts as an equivalence of "be" in English.
- Not using "在" would be like saying "the school bus coming"