When you study about the particle が alone, it seems simple. It marks the subject of a sentence. But when you need to decide between は and が, the whole thing gets messy.
First things first. What does が do?
It marks the subject of a sentence. The English nomenclature might be confusing because “topic” and “subject” can be used interchangeably. In Japanese, they refer to two different concepts.
The main difference is that は marks what comes AFTER it and が what comes BEFORE it. Only the context will tell you which one to use it. Here are some common situations when you’ll need either of those:
- your friend misunderstood you and you want to be clear about the subject. が
I’m Bonnie, not her!
- the topic is already known (or not), but you want to provide some extra/specific information about it. が
Bonnie (the topic) can’t read kanji (the subject) (The way I think of it is when you have two nouns in one sentence, one of them 99% of time is the topic and the other one is extra information)
- You already know what the topic is and there’s no need to state it again. You want to focus on different things in your conversation. は
I’m talking about the food I’ve made, and suddenly someone asks a specific question about it. “My food is blah blah blah…” (I’m talking about the topic – my food) “Wait up! What about this thing here?” did they ask me about the topic? No! We already know it. Did something else turn out to be important? Yes? An ingredient.
Remember this example? これはチョコレートです。 The important part here is chocolate. Chocolate was the ingredient that made my dish delicious. Now, let’s state the same thing using particle が.
チョコレートが重要な成分です。(chocolate is the important ingredient)
The sentence alone doesn’t tell us much. Let’s think of a context that would make things a bit more clearer.
You’re talking with your friends about the dish you’ve made. One of them asks: “Hey, what makes your dish so delicious?”
- What’s the TOPIC of your conversation? – Your dish
Now, you want to provide the subject of your sentence. The essential part of your dish. You say: “Oh, chocolate makes it so delicious.”
- What’s the SUBJECT of your sentence? – Chocolate
What we did here, we put the emphasized word in a different position.
Why? Because the conversation took a slightly different course.
“Hey what’s this thing here? It makes the whole meal delicious.” You say: “Oh, it’s chocolate” これはチョコレートです。Here, we pointed to a specific thing that is important. We want to know what this specific thing is. We’re not interested in the topic anymore because we know it. The emphasis is put somewhere else (on the ingredient) in this case.
“Hey, what makes your dish so delicious?” “Oh, chocolate makes it so delicious.” In this case, we actually asked about the thing and at the same time we established the topic of our conversation.
What makes – the answer to that will be the subject of our sentence が
Your dish – the topic of our conversation は
You can also ask yourself these questions:
- Do I need to state the topic? Do people know what I’m talking about? No? Then use は
- Do we know what the topic is? Yes? Then omit the は. There’s no need to keep telling people every second what we’re talking about…As for my food, I used this and that. As for my food, it took me 10 minutes to prepare it. As for my food….
- Do I need to provide extra (a bit more specific) information about the topic? Is there going to be a second noun in my sentence? Yes? Then use が for that second noun (it’s a soft rule)
- Sally wants to get a dog. Two nouns. Sally and dog.
- Am I using a WH-question word? Who? What, When? Yes? Then use が
- Am I contrasting things? Today is nice (but yesterday it wasn’t). I’m contrasting today and yesterday. Use は (note that if you’ve been talking about the yesterday’s weather (it was so rainy, cold, and stormy yesterday!) and you want to contrast it with today’s weather, you don’t need to say “… but yesterday it wasn’t.” It’s already clear from the context.)
I hope it will help some of you. However, the context will tell you which one to use. The last example! You’re describing a conference room you’ve booked to your boss. The topic is the conference room.
As for the conference room, it is big. 会議室は大きいです。(we’ve just stated the topic)
The walls are white. (Am I stating a new topic? No. I’m giving specific information about the topic) 壁が白いです。
There is a table. テーブルがあります。
If there’s anything you want to correct, feel free to do so. I’m no expert!