Possible Duplicate:
What’s the difference between wa (は) and ga (が)?
I've been trying to wrap my head around the は/が differences, and I'm trying to figure out the differences between the thematic は and the neutral descriptive が.
Take for example.
日本語の授業は面白いです。
vs
日本語の授業が面白いです。
Can someone tell me the difference between the switching of the particles?
The key to understanding は is to understand how a sentence ties back to the discourse. This is where the "topic" comes in. Some linguists will claim that all Japanese sentences have a topic, even if it's implicit and unstated.
If you're asked:
日本語の授業についてどう思いますか？
What do you think about your Japanese lessons?
what ties back to the discourse is "日本語の授業", so it will be marked with は:
日本語の授業は面白いです
On the other hand, if somebody says to you:
今日は機嫌がいいですね
You're in a good mood today
what ties back to the discourse is not "日本語の授業", rather, it's the cause-and-effect relationship of why you're in a good mood. Using the sentence with は will sound strange, as if you're switching topics. Rather, to explain why you're in a good mood (staying on topic, although the topic is never explicitly stated), you might say:
日本語の授業が面白いです
Note that this (has a reading which) is not an exhaustive-listing が. I disagree with the answers that claim that there's no "neutral description" が for this sentence because 面白い is not state-change.
Just to preempt possible comments, this sentence does sounds slightly uncommon. Usually it is more idiomatic to add a の/ん, which is another way to tie a sentence into a discourse.
はい、日本語の授業が面白いんです
Yes, my Japanese classes are fun!
So to your question in the comments about whether this が is exhaustive-listing or neutral-description, my answer is: "It can be both".
The two sentences are both valid sentences, but would be used in entirely different contexts.
In the は example, you are highlighting the topic of your conversation. Suppose you are in the cafeteria with your friend, and you want to say "Japanese class is interesting, isn't it." You would use particle は thus:
日本語の授業は面白いですね。
You are introducing a new topic of conversation, and so the は particle hilights what it is you are talking about. A literal translation of this is something like "Speaking about Japanese Class, interesting, right?" I find using "Speaking about" as a translation for は helps to remember it.
が is used to highlight the specific subject of a sentence, when you want to clarify what it is you are talking about inside of a specific context. For example, your friend is asking you about the classes you are taking at college:
大学の授業はどっちが面白いですか。
"Speaking about your college classes, which is interesting?" In this case, replying using the sentence above with は would sound unnatural, like you are changing the subject (which you are because は introduces a new topic!). Instead, you would reply naturally:
日本語の授業が面白い。
This は・が distinction extends to other things, for example the simple "I like" sentence. Say your friends are talking about what fruits they like, and you want to chime in by telling them you like apples:
私はりんごが好きです。
"Speaking about me, apples are liked." In this case, the topic of conversation is you, and what you like. The specific subject of your sentence is apples - that you like them. You would drop the 私は if someone explicitly asked you which fruit you like - you don't need to change the topic because they are already talking about you.
はis A more of a topic marker while が is not. For instance こんにちは marks the topic of "This day".
As you probably know, は／が distinction can fill entire grammar dictionaries; I know, I have one. So there are many facets to have they differ. But one way I try to remember is that は is the topic marker and が is more of a specific indicator. So with your examples it would be like
- 日本語の授業は面白いです。 → "Speaking of"/"As for" (my) Japanese class, it is interesting. This is looking only at the frame of reference of the class (the class is the topic). Nothing else is considered.
- 日本語の授業が面白いです。 → "The Japanese class is what is interesting."/Japanese is the specific class (or thing) (out of possibly others) that is interesting." Note that in this kind of sentence, the topic being discussed (whether literally or implied) is probably different. The discussion might have been about different classes, and you single out one as interesting. Or it might have been about things you find interesting, and you pinpoint the Japanese class.
So I try to remember that one of が's major functions it to point to one specific example that the description applies to.
The difficulty with your example is partly that this が is not neutral description. As Sindry commented, this one is "exclusive listing". From Kuno's book (and quoted here):
"Sentences of neutral description present an objectively observable action, existence, or temporary state as a new event."
Somewhat more particularly:
neutral description only works with action verbs, existential verbs, and adjectives/nominal adjectives that represent state change
面白い does not represent state change, it's quite clearly referring to a state. As a general rule, 形容詞 can only be neutral description in the sentence-final ending in cases where something changes in front of your eyes (color change, for example).
As mentioned above, neutral description-が is used for describing something that is actively happening. This limits the usage basically to situations where you watch something happen, and comment on it, or situations that could be extrapolated from that theme. There is also the slightly odd exception of the existential verbs: aru and iru, which can also work with a 'neutral descriptive'-が.
Thematic-は, on the other hand, is used to bring things up again in the conversation. If we talked for awhile about A, then shifted to talking about B (or if A was a minor point in talking about B), one of us could shift the topic of conversation by starting out with "Aは。。。".
