Tae Kim's Guide explains it pretty well, but I'll add to what I know about the differences.Originally Posted by Moon Rabbits
Overall が has many more uses than は. As most know は is referred to as the topic marker whereas が is the subject marker. Tae Kim, in her guide, says that defining が as a subject marker can be misleading, I agree. How my prof explained it to us is that は expresses shared knowledge between the speaker and the listener, whereas が expresses that the information is new to the listener or that the speaker believes the is new to the listener. In this case, Tae Kim's redefinition of が as an unknown marker is apt. Returning to your examples:
私は学生。
Here it is understood that both the speaker and the listener are aware that the speaker is a student.
私が学生。
Here it is understood that the listener did not know that the speaker was a student.
が also functions as marking an unknown in questions as well. When the subject is a question word, then が always follows it.
Ex: どこがいぬいますか。 (Where is the dog?)
In this case, the location of the dog is unknown to the speaker.
If the question words follows the topic, then you use は.
Ex: じむしつはどこですか。 (Where is the business office)
In this case, the topic, business office, is known to the speaker therefore is marked with は.
Also, after the subject has been mentioned, you can use は to refer to the same thing.
Ex:
A:あそこにねこがいますね。 (There is a cat over there)
B:それはくらいねこですか。 (Is it a black cat?)
A-san reveal the information about the cat to B-san (this is new information to B-san). B-san, now knowing of the cat's existence, uses は to mark it.
は and が can be used in the same sentence as well.
Ex: 田中さんは目があおいです。 (lit: As for Tanaka-san, he has blue eyes)
The topic here is Tanaka-san, though the subject of the verb copula is eyes.
*This is not to be mistaken for: 田中さんの目はあおいです。 (lit: As for Tanaka-san's eyes, they are blue). Even though to English speakers there would be very little difference between the two, also the fact that the more literally translation of the former is rather clumbsy in English, there is a slight difference between the two.*
There are a few more examples where you would use が with は but those are for more complex sentences that use modifying clauses. I was about to write about them but then realized I am more or less vomiting all that I know and it might prove to be TMI. If not, just say and I can try to explain those too. (Also if I am wrong, please correct me for my own sake as well as everyone else's. I profess that I am only a beginner like everyone else. Heck, I barely passed my Japanese class).
I hope this makes sense. It is part from memory, part from my text book (Nakama). Mostly the examples from my text book. If anyone notices any mistakes, please tell me!
As for が it can have other uses too. が also works with intransitive verbs as well, or when referring to skill or abilities. So when you are talking about being skillful at something (上手), suck at something (下手), like something (好き) or understand something (分かる), you use が to mark that which you skillful[or good] (at)/poor (at)/like/understand.
Finally, が can be used to contrast two sentences. Think of it like a weak version of "but".
There are many more uses of は and が, though you will come more and more across them as you further your studies. Heck, I am sure I have not seen the end of them yet. -__-; *should brush up on stuff before September*
EDIT:
As for も, it can be used with question words to form a negative noun. Okay, that sounds odd but here is what I mean:
何も - nothing
だれも - no one
いつも - never (can also be used in the affirmative sense to mean always)
どこも - nowhere
も can also be used to express a lack of preference.
東京も京都もおもしろい所です。 (Both Tokyo and Kyoto are interesting places)
There are probably more uses of the particle も that I am not aware of. Still a newb to the language myself. ^__^;;;
Reply With Quote
