In English, the identification of a subject is usually done via context, or knowing which information modifies which, such as when an auxiliary verb (is, are, am, etc.) is referring to someone or something.In Japanese, the same is also true. However, it is quite easier to point out, since there are two major particles that are used precisely to point out a subject in a sentence or clause. These are none other than Wa (は) and Ga (が), and in this article we shall briefly discuss its uses and applications, as well as the core differences between the two.
Understanding Wa (は)
Those who already know Hiragana should immediately notice the apparent “error” in the representation of Wa as は. This is in fact, not a typo, and Wa is actually shown as Ha, when it is inscribed in written form. This is a rollover rule from how Wa was originally written in older Japanese prior to 1946, before the official revision of the modern Japanese language that is taught today. Long story short, Wa is Ha in written form, because it was already the default letter used for a very long time.
As we have mentioned in the introduction, Wa is used primarily as a subject indicator. Anything that will generally be related or directed to the rest of the entire statement afterward should be enclosed with this particle. This is typically the reason why Wa (as a subject marker) is only used once in a sentence. This is also the reason why many Japanese learning textbooks try to provide the literal translation of Wa using “as for” (e.g. as for Mr. Tanaka - Tanaka-san wa - 田中さんは )
I am John. / Watashi wa Jon desu. / 私はジョンです。
He is a doctor. / Kare wa isha desu. / 彼は医者です。
(The) shoe is black. / Kutsu wa kuro-i desu. / 靴は黒いです。
Tempura is expensive. / Tenpura wa takai desu. / てんぷらは高いです。
(A) dog is an animal. / Inu wa doubutsu desu. / 犬は動物です。
Because Wa is a general topic indicator, it does not strictly have to adhere to a literal meaning. Which means the information stated by the predicate could instead answer a question, or confirm a query that is related to the subject understood by both speakers (the word inside Wa). The sentence could sound a bit weird if translated word-per-word this way. But when given context, they’re perfectly okay to speak or write. One simple example of this would be:
I will have coffee / Watashi wa koohi desu. / 私はコーヒーです。
When translated word-per-word based on our prior examples, this should have been “I am coffee”, which, definitely does not sound right to any casual listener. Instead, this response answers a question of which drink will the subject have. Hence, “as for “ the subject, “this will be the option”, as agreed upon by both speakers.
Understanding Ga (が)
When we attempt to determine who did a certain action with a question, we usually end up pointing directly towards the subject. Thus, Wa is generally usable as the sole subject marker for most situations. But what if you need to specify, or confirm who or which exactly will that statement or action, be related to?
That is the job of Ga (が). If Wa is the general subject marker, then Ga is the specific subject marker. It specifies, within a contextualized set of possible subjects, which exactly would be directed to the information indicated by the predicate. Because of this, Ga can easily be used multiple times for different separate clauses, unlike the single general marker Wa.
Structure-wise, Ga is used almost the same as Wa. In fact, given free context, we could use the exact same set of examples earlier. Simply replace Wa with Ga for each sentence just to show how they changed with the particle switch. Take a look at some of these:
I am John. / Watashi ga Jon desu. / 私がジョンです。
Instead of just simply introducing oneself as “John”, the speaker is now specifying that out of all the people within a speculated set of persons, he is “the John” among them.
(The) shoe is black. / Kutsu ga kuro-i desu. / 靴が黒いです。
Instead of just remarking that the shoe as colored black, it is revealed that there are actually several items that have different colors, and that it is “the shoe”, that is specifically colored black.
Tempura is expensive. / Tenpura ga takai desu. / てんぷらが高いです。Instead of just being disappointed at the seemingly high price of tempura, there is now a hint that a set of other food items exist: the menu where “the tempura” is shown to be the most expensive item available.
Should I use Wa (は) or Ga (が)?
If you are simply referring to a general subject, then Wa. If you need to let your listener know that the subject is a precise choice for an action or statement, then Ga. That being said, we can further specify the situations where the use of either Wa or Ga may be more appropriate. In these double-use scenarios, the importance of one over the other in their respective functions, become more apparent:
1. Stating the subject of a clause - if the subject is within a separate clause within a bigger sentence, then Ga is automatically used.
ex. Mr. Tanaka has a car - Tanaka-san wa kuruma ga arimasu
田中さんは車があります。([As for] Mr. Tanaka, [He] has a car)
2. Stating the doer of the verb related to the subject - if the subject is being pointed to as the one responsible for the general subject involved.
ex. I will prepare the sandwiches - Sandoicchi wa Watashi ga shitaku shimasu サンドイッチは私が支度します ([As for] the sandwiches, I will prepare [them])
Hopefully, this gives you a better idea on how Wa (は) and Ga (が) actually function in a basic Japanese sentence. There are more complex examples of course, but they require even more prerequisites, so we would simply have to revisit them later on.