Differentiating が or は(pronounced wa) can't be defined by rules. They aren't the same kind of particle, and がは and はが are consequently impossible. Particles show function, so focus on this. This lesson does not discuss all the usages of the two. This lesson simply gives you the gist of how to use the two in basic sentences.
In this lesson, many adjectives and some verbs will be used in the examples. Because we have not discussed how to conjugate more than the basic forms of things (which involves doing nothing) and have not learned how to deal with adjectives or verbs, they will only be used in the non-past tense, which again, involves no additional grammar know-how.
The grammatical subject of a Japanese sentence may be marked by the particle が. However, the usages of the particle が, how they relate to each other, and how they relate to other similar grammatical patterns such as the particle は to follow are so complex that there is no way it can all be mentioned in this introductory lesson. So, this lesson should only be seen as a very basic introduction to these particles.
A subject is what a predicate "statement" is about. This concept of a "subject" is tied closely to whether something is a "new" piece of information versus a topic of discussion that has to some degree gone past the stage of just being a new piece of information (contrasting with は). Consequently, this means that が is perfect to show the existence of something. When telling someone that something exists, you aren't assuming that they know about it.
Literally: (Your) head is good.
The waves are high.
The sky is blue/It is the sky which is blue.
Nuance Note: が may particularly point something out as the focus of one's statement, and in doing so, a small pause typically follows が. Commas aren't necessary for this, but you may see them used here.
New information does not equate to contrast. It's not that Ex. 4. equates to the bird is blue or the bird is blue. Providing details is something we do all the time in a conversation, but it's not the case that we make each detail a topic of discussion. If we were to do that, then we would address each detail as the topics of separate statements. が does have an emphatic usage, but in order to know how the particle is really working, context is needed. Context is also, unfortunately, needed to truly distinguish it from the particle は discussed below.
The bird is red.
Sense of Discovery
が may show what's found out, whether it be the beginning of a story, discovery itself, etc.
Ah, this is snow!
Conversations have a topic, which is somewhat familiar to the speaker and listener(s). は doesn't show new information. So, "AはBだ" shows something of conversational value. To better show how this differs with "AがBだ", compare the following.
6. リンゴが赤い。 7. リンゴは赤い。
The apple is red. Apples are red/an apple is red/as for apples, they are red.
He is bad.
As for him, he's bad.
In 7, the listener(s) may not know him or about this "bad" quality. In 8, both the speaker and listener(s) know the topic, him, very well.
は and が are called the topic and subject markers respectively with the understanding that if either is absent, the topic and subject may coincide with each other. If は were replaced by が, が would change the topic into the focus. Focus doesn't mean contrasting with anything. Rather, it draws attention to a statement, and this is in line with everything we've seen about が thus far. Try not to dwell on the names of these particles. Topic and subject don't help us a whole lot in using these particles perfectly 100% of the time, but they do help us grasp them well for the meantime.
Intonation Note: There is normally a small pause that accompanies は when showing a topic.
10. リンゴは小さい。(Apples would already be the topic of discussion)
Apples are small.
Tea for me.
Meaning Note: This sentence doesn't mean "I am tea". は doesn't specifically link the subject with the verb.
Topic は Subject が X
X is an adjective or verb, and the topic and subject can flip depending on importance. Typically, though, this is the most natural ordering. This pattern is used to discuss a matter concerning the topic.
As for elephants, their noses are long.
Japan has many shrines.
Expressing Nationality and Occupation
は is used when expressing nationality or occupation.
|Nationalities||Occupations (Plain)|| Occupations (Polite)|
| フランス人 ＝ French person|| 教師（きょうし） ＝ Teacher|| 先生 ＝ Teacher|
| アメリカ人 ＝ American person||学生 ＝ Student|| 学生さん ＝ Student |
|イギリス人 ＝ English person|| 医者（いしゃ） ＝ Doctor||お医者さん ＝ Doctor|
|中国人 ＝ Chinese person||銀行員（ぎんこういん） ＝ Banker||銀行員さん ＝ Banker|
Usage Note: The polite occupations aren't used in reference to oneself.
He is Japanese.
She is Chinese.
She is a teacher.
Questions:Translate the following.
1. I'm not Japanese. (Polite)
2. I am Chinese.
3. Yes, the book is difficult.
Part II: Fill in the appropriate particles.
There are three apples. That's a red apple.
That person (over there) is a student.