The difference between 「は」 and 「が」
This, essentially, is the difference between は (wa) and が (ga) . let’s translate these sentences into Japanese.
私はこういちです。 I am Koichi
私がこういちです。 I am Koichi
The translation is the same, so what’s the difference? Here’s where people usually get confused. First, let’s take a look at は and が, and what they mean.
は emphasizes what comes after it and talks about something
が emphasizes what comes before it and identifies something
So, what’s the difference between these two sentences?
私はこういちです。I am Koichi. This sentence uses は, so the important thing is what comes after it. The important thing is that my name is Koichi (and not that I am the Koichi you’re talking about).
私がこういちです。I am Koichi. This sentences uses the が particle, so the important thing is what comes before the が. The important thing here is that I am the Koichi you are talking about (remember, は talks about something). We are identifying something.
Let’s look at another example.
I’m introducing myself. I would say:
私はこういちです。 I am Koichi. The important part is that my name is Koichi.
Now we’re in a crowded room, and the announcer comes on and says “Someone named Koichi left their car lights on. Who here is Koichi?”
Then you’d reply: 私がこういちです, because you need to identify that you are the Koichi they’re talking about.
When it comes down to it, though, it can be summed to these two points:
は emphasizes what comes after it and talks about something
が emphasizes what comes before it and identifies something
すしが好きです = I like Sushi
We’re identifying the Sushi.
すしは好きです = I like Sushi / It is the sushi that I like
We’ve already identified the sushi, we’re already talking about the sushi, so there’s no need to identify it. Now we’re just talking about the sushi, so は is the particle to use.
Practice a lot, and make sure you study every single instance of は and が that you run into and figure out why は is used or why が is used.
Related Post:
Learn Japanese Particles: Lesson 2
Usage of Japanese Particles: を and は