Why This Lesson Matters
The difference between は and が is one of the most discussed — and most misunderstood — points in Japanese grammar. Many textbooks teach は as a “subject marker,” which leads to persistent confusion. This lesson corrects that misconception and builds a clear, practical understanding of what each particle actually does.
The Core Distinction
| Particle | Type | Grammatical role |
|---|---|---|
| が | Case particle (格助詞) | Marks the grammatical subject — who or what performs the action |
| は | Adverbial particle (副助詞) | Marks the topic — what the sentence is about |
💡 The most important point: は is not a subject marker. It marks the topic — and the topic can be the subject, the object, a location, or almost anything else. は and が are not interchangeable; they do different jobs entirely.
Part 1: What Does が Do?
が marks the grammatical subject — the person or thing that performs or experiences the action. It tends to appear when:
- Identifying who does something (answering だれが…?)
- Presenting new or focused information
- Using question words (なにが, だれが, どこが)
Identifying Who Does the Action
だれがこのすしをたべますか？ → Who will eat this sushi? 私がこのすしをたべます。 → I am the one who will eat this sushi.
が here has a identifying / spotlighting effect — it answers “who?” and singles out the subject from other possibilities.
Compare with は:
私はこのすしをたべます。 → As for me, I’ll eat this sushi.
The は version does not specifically answer “who?” — it frames “me” as the topic and tells you what I will do.
With Question Words
が always pairs with question words asking about the subject:
| Japanese | English |
|---|---|
| なにがへやにありますか？ | What is in the room? |
| まんがとおもちゃがあります。 | There are manga and toys. |
| だれが一番つよいですか？ | Who is the strongest? |
| どこがいたいですか？ | Where does it hurt? |
💡 Rule: When a question word (だれ, なに, どこ, etc.) is the subject of the sentence, it always takes が — never は.
Part 2: What Does は Do?
は marks the topic — the thing the speaker is choosing to talk about. The rest of the sentence provides information about that topic. は has two main functions in natural speech:
Function 1 — Topic Marking
は sets the stage: it tells the listener what the sentence is going to be about. Everything after は is a comment on that topic.
あなたは何をしますか？ → As for you, what will you do? 私はすしを食べます。 → As for me, I’ll eat sushi.
In conversation, this is the most common function of は — establishing a topic and making a statement about it.
Function 2 — Contrast
は also creates implicit contrast — a sense of “this one, as opposed to others.” Even a simple sentence like 私は食べます carries the undercurrent: “I will (even if others won’t)” or “I at least will.”
他の人は食べないけど、私は食べる。 Others won’t eat it, but I will.
Here, は appears twice — each instance creating a contrast between two things. が would not work here, because the point is not to identify who does it, but to compare two different subjects.
Part 3: Topicalizing — How は Interacts with Other Particles
One of the unique powers of は is that it can replace or attach to other particles to shift any noun into the topic position. The rules for how this works depend on the particle.
The Topicalization Rules
| Original particle | Rule | Result |
|---|---|---|
| が | Replaced by は | Tinaが → Tinaは |
| を | Replaced by は | この本を → この本は |
| に / へ (motion verbs: 行く, 来る) | Replaced by は | 学校に → 学校は |
| に / へ (non-motion verbs) | は added after | 東京に → 東京には |
| で | は added after | 城で → 城では |
| と, から, まで | は added after | 駅から → 駅からは |
💡 Simple rule: が and を disappear when は takes over. All other particles stay and は is added after them.
Worked Example: Topicalizing the Same Sentence
Start with a neutral sentence — no topic marked:
「Tina が 城で この本を 読む。」 Tina reads this book in the castle.
① Topicalize Tina (the subject):
「Tina は 城で この本を 読む。」 As for Tina, she reads this book in the castle. → が is replaced by は
② Topicalize the place (で):
「城では Tina が この本を 読む。」 As for the castle, Tina reads this book there. → で stays, は is added → では
③ Topicalize the object (を):
「この本は Tina が 城で 読む。」 As for this book, Tina reads it in the castle. → を is replaced by は
More Examples
Place as topic (では):
彼が台所でコーヒーを飲んでいる。→ He is drinking coffee in the kitchen. 台所では、彼がコーヒーを飲んでいる。→ As for the kitchen, he is drinking coffee there.
Object as topic (を → は):
Mikaが本屋でこの本を買った。→ Mika bought this book at the bookstore. この本は、Mikaが本屋で買った。→ As for this book, Mika bought it at the bookstore.
Destination as topic (に → は or には):
金持ちの子どもがこの学校に来る。→ Rich kids come to this school. この学校には、金持ちの子どもが来る。→ As for this school, rich kids come here.
💡 With motion verbs (来る, 行く), に is sometimes dropped entirely when は replaces it: この学校は、金持ちの子どもが来る. Both この学校は and この学校には are acceptable — には is slightly more formal and precise.
Part 4: が vs は in Natural Sentences
The Information Focus Difference
The choice between が and は is closely tied to what information is new vs already known.
| Particle | Information type | Feeling |
|---|---|---|
| が | New / focused / being introduced | “Here is the answer to who/what” |
| は | Known / being discussed / contrasted | “Here is more about what we’re talking about” |
Side-by-Side Comparison
Example 1 — Identifying vs Discussing
Alexが日本にきます。 Alex is the one coming to Japan. (answering: who is coming?) → が identifies Alex as the specific person. New information.
Alexは日本にきます。 As for Alex, he is coming to Japan. → は makes Alex the topic. Either continuing a conversation about Alex, or implying contrast with others.
Example 2 — Introducing vs Referring Back
猫が家にいる。 There’s a cat at home. → が introduces the cat as new information. The cat is being pointed out for the first time.
猫は家にいる。 As for the cat, it’s at home. → は assumes the cat is already known to the listener. The sentence is about its location or status — possibly contrasting with something else (e.g., the dog is outside, but the cat is home).
Example 3 — Event vs Context
あのバカがここに来た。 That idiot showed up. → が highlights the arrival as a new event. Feeling: surprise, reaction, spotlighting who arrived.
あのバカはここに来た。 As for that idiot, he showed up. → は sets him as the topic with a contrast nuance: “he (at least) came” — implying others maybe didn’t.
In dialogue:
A: だれが来た？→ Who came? B: あのバカが来た。→ That idiot came. (identifying the arrival)
A: みんな来た？→ Did everyone come? B: あのバカは来た。(けど他はまだ) → That idiot came. (but others haven’t yet — contrast)
Part 5: Topic Dropping in Spoken Japanese
In natural conversation, は — and the topic it marks — is frequently omitted when the topic is already understood from context.
Q: スコットくんは今から何をするの？→ What are you going to do now, Scott? A: 東京に行く。→ Going to Tokyo.
The full answer would be 私は東京に行く, but 私は is dropped because both speakers already know who the topic is. This is extremely common in everyday Japanese and is a sign of natural fluency — not grammatical laziness.
Summary
Core Functions
| Particle | Role | Use when… |
|---|---|---|
| が | Subject / focus marker | Identifying who does something; answering だれが/なにが; new information |
| は | Topic / contrast marker | Setting what the sentence is about; making comparisons; known information |
Topicalization Rules
| Original particle | What happens with は |
|---|---|
| が / を | Replaced by は |
| に / へ (motion verb) | Replaced by は (に sometimes dropped) |
| に / へ (non-motion) | には |
| で | では |
| と / から / まで | とは / からは / までは |
Key Reminders
- は is not a subject marker — that is が’s job
- は can topicalize any noun — subject, object, location, etc.
- が answers “who/what does it” — は answers “what are we talking about”
- は implies contrast — even when not explicitly stated
- In conversation, は is often dropped when the topic is obvious
Practice
Choose は or が:
- ＿＿＿が食べますか？(Who will eat?)
- 私＿＿＿すしを食べます。(As for me, I’ll eat sushi.)
- 猫＿＿＿かわいいですが、犬＿＿＿かしこいです。(Cats are cute, but dogs are smart.)
- なに＿＿＿ほしいですか？(What do you want?)
- この映画＿＿＿もう見ました。(As for this movie, I’ve already seen it.)
Answers: 1. だれが 2. 私は 3. 猫は、犬は 4. なにが 5. この映画は