Many people who start to learn Japanese get confused when they encounter the words は and が. These particles can be a very efficient way of describing a variety of situations. However, the subtlety can lead to some confusion, so please keep reading for a clarification on these very important particles.
The Basic Idea of は vs. が Topic particle はThis particle identifies the topic of the sentence. In Japanese you can first identify the general thing you’re talking about, and then provide the relevant information about it.
Identifier particle がIf we don’t know specifically what the topic is, we can instead use が. If we want to ask, “Who is the teacher?”, we need some kind of identifying particle, because the identity of the teacher is not yet known. If we used the topic particle, the question would turn into, “As for who, is teacher?” and that doesn’t work because “who” is not a specific person. That is why we need「が」 .
More Details は Indicates Contrastオレンジは好すきです。
オレンジが好すきです。
*Vocabulary: オレンジ = orange, 好すき = to like
It may seem as though the above phrases mean the same. However, there is one big difference. 「オレンジは好すき」 means the speaker likes oranges, but perhaps doesn’t like other fruit.
If you say, 「オレンジが好すき」, this just means you like oranges more than other fruits.
私はオレンジが好すきです。
Don’t confuse the topic particle and contrast functions. The above sentence can be translated as, “As for me, orange is the one I like.” In this sentence, は is just a topic particle.
が Indicates New Information雨あめが降ふっています。
雨あめは降ふっています。
*Vocabulary: 雨あめ = rain, 降ふる = to fall
Which phrase should you use when you notice that it started raining outside? There is also an important distinction to be made here. The answer is 「雨あめが降ふっています」 because there is some information that is new to the speaker. When you first realise something is happening or true, you have to use が. For example, if you then realise it’s snow instead of rain, you would have to say, 「雨あめ(old information)は降ふっていません。雪ゆき(new information)が降ふっています。」
天てん気きはどうですか？(How is the weather?)
雨あめが降ふっています。 / 雨あめは降ふっています。
In this example, if somebody asks, “How is the weather?” and you open a window in order to look at the weather, 「雨あめが降ふっています」 is the correct phrase because you have only just noticed that it is raining. If you want to say, “It started raining, but not snowing,” it will be something like 「雨あめは降ふっていますが、雪ゆきは降ふっていません」 because this is a contrast. If someone asks you, 「雨あめは降ふっていますか？」 instead, 「雨あめは降ふっています」 is the proper response because the topic of the question is already known to be 雨あめ.
Grammatical Rules for は vs. が (for Intermediate or Higher)は and が also have specific rules dictating their grammar. Please see below for some examples.
In Noun Clauses, が is Common雨あめが嫌きらいな人ひとは私わたしです (I’m the one who doesn’t like rain)。
オレンジが好すきなのは私わたしです（I’m the one who likes oranges）.
In Subordinate Clauses, が is Common, Except for the FollowingLonger sentences involving は and が may start to trip you up. A rule of thumb is that が is used mainly in subordinate clauses. There are only some exceptions, which you can see below.
When は is Used for Contrastお寿司すしは美味おいしいけど、納豆なっとうは美味しくない (Sushi is delicious, but Natto is not delicious)。
これは面白おもしろいけど、あれは面白おもしろくない (this is interesting, but that is not interesting)。
When a Main and a Subordinate Clause Have the Same Subjectお寿司すしは美味おいしくて、売うり切きれました (Sushi was delicious and was sold out)。
このマンガは面白おもしろくて、有名ゆうめいになりました (This manga is interesting and became popular).
When a Subordinate Clause Expresses a Reason for a Main Clause明日あしたは日曜にちようなので、買かい物ものに行いきます(Since tomorrow is Sunday, I will go shopping)。
明日あしたは休やすみなので、野や球きゅうをします(Since tomorrow is day off, I will play baseball)。