分からないで

⚠️ This is a translation of my German article “Das は-が-Dilemma” using machine translation.

Among the most difficult topics for beginners, the difference between は and が is surely near the top. Both particles seem to mark the subject in some way—but then again, they don’t. We’re often told that は marks the topic and が marks the subject—but in English, the subject is also frequently what a sentence is “about,” so the distinction can feel blurry.

In this article, I’ll try to shed some light on the issue and explain why it is particularly confusing for native English speakers.

Fair warning: things are about to get theoretical. To explain the difference between は and が, we first need to introduce a few key concepts.

Particle categories in Japanese

Japanese particles belong to different categories.

• が is a case particle. Case particles mark the grammatical role of a noun within a sentence. They show how the noun relates to the predicate, whether that predicate is a verb or an adjective.
• は, on the other hand, is a discourse particle. Discourse particles indicate how a noun functions within the flow of communication—that is, how it relates to previous sentences and to shared context.

There are other particle categories as well, but they aren’t important for our purposes here.

What is “case”?

Grammatical case describes the logical role of a noun in a sentence. Think of actors that take different roles in a play. Cure Dolly Sensei made a very good video on this (on YouTube).

In Japanese, this is relatively easy to identify because the particle following the noun makes this role explicit:

タナカさんが　駅えきで　９時じに　ナイフで　先生せんせいを　殺ころした。

Here, the nouns take on the following roles:

• タナカさんが stands above the scene—he is the “perpetrator” (the subject), marked by が. In English, the subject determines the form of the verb.
• 先生を lies on the ground—he is the “victim” (the object), marked by を.
• The remaining particles provide context: where (駅で), when (９時に), and with what (ナイフで).

Modern English has largely lost its case system. The role of a noun in a sentence is determined by a combination of word order and prepositions.

Mr. Tanaka (S) killed (V) the teacher (O) with a knife at the station at 9 o’clock.

We can also say “at 9 o’clock with a knife at the station” without changing the meaning, but we cannot switch subject and object. “The teacher killed Mr. Tanaka” clearly describes a completely different situation.

In Japanese, however, you can freely rearrange the constituents of a sentence, as long as the predicate remains at the end:

９時に　ナイフで　先生を　タナカさんが　駅で　殺した。

This sentence is perfectly grammatical. The teacher is still unmistakably the victim, because を marks them as the object.

What is “discourse”?

Discourse refers to a system of statements and interpretations through which information is structured and meaning is created. That sounds abstract, so let’s look at an example.

The two main discourse particles in Japanese are は and も. Their basic functions can be described like this:

• は singles out an element and establishes it as the frame or background for what follows. It signals: “We’re talking about this now.”
• も adds an element to an existing set. It signals: “This belongs here as well.”

In this sense, the two are opposites: は restricts, while も expands.

• お父とうさんと　お母かあさんが　バナナを　たべた。
• お母さんは　りんごも　たべた。

The first sentence introduces a new situation: father and mother ate bananas.

The second sentence shifts the attention. Now we are talking specifically about the mother, and we add apples to what she ate. This second sentence builds directly on the first.

In simple terms, this is what discourse is: the way individual statements connect and build on one another.

Topic and comment

Now that we’ve seen how は and も structure relationships between sentences, let’s look at how information is structured within a single sentence.

Any statement can roughly be divided into two parts:

• a part that connects to what is already known
• a part that provides new or relevant information

In linguistics, these are called:

• Topic: what the sentence is about
• Comment: what is said about the topic

A simple test:

• “Tell me something about X.” → X is the topic
• Everything else is the comment

You may also encounter other terms, such as theme and rheme, background and focus, or topic prominence. Japanese is a so called topic-prominent language, while English is subject-prominent.

It’s important to understand that topic and comment are not grammatical roles. They do not tell us if something is a subject or an object; they describe how information is organized.

Consider this example:

1. A prince lived in England.
2. The prince loved a miller’s daughter.
3. He had a strict father.
4. The father did not like the miller’s daughter.

Except for the first sentence, we build on known information and add something new to the common knowledge. In Germanic languages, one common way to signal this is to place it at the beginning of the sentence. This is the topic, here it's highlighted by underscoring. However, in English, this position is also the grammatical slot of the subject, so topic and subject tend to overlap—making it harder to distinguish between the two.

Japanese often works similarly, but marks the topic explicitly with は:

1. イギリスに　王子おうじさまが　住すんでいた。
2. 王子さまは　こなやの　むすめを　愛あいしていた。
3. きびしい　父親ちちおやが　いた。
4. 父親は　こなやの　むすめを　嫌きらっていた。

Here’s what happens:

• Sentence 1: A new situation is introduced—everything is new.
• Sentence 2: 王子さま is marked with は; we continue talking about the prince.
• Sentence 3: No は appears—this is perfectly normal; the topic remains implicit.
• Sentence 4: 父親 becomes the new topic, marked with は.

Unlike English, Japanese does not require to restate the subject each time. Once a topic is established, it remains active until a new one is introduced.

Known vs. new information

Whether something is “known” or “new” depends on the listener, not the speaker.

For example:

“My little sister now lives in London.”

• For someone who already knows I have a sister, “my little sister” is known information.
• For someone who doesn’t, it is new information.

The sentence itself does not change—but its information structure does.

So:

• The topic is something that the listener can relate to
• The comment is what is new or relevant to him

This distinction is communicative, not grammatical.

The は–が dilemma

Before going further, here’s a useful rule to remember:

は never marks the subject.

This is a lie of course—but it’s a helpful one.

So why does は often feel like a subject marker?

Because in many sentences, the topic and the subject are the same. This is typically the case in English—and often in Japanese as well.

That’s where the confusion arises: は looks like a subject marker, but it isn’t.

What は actually marks

は marks the starting point of the statement—the element the sentence is about.

In other words:

• は tells us what we are talking about
• not who is performing the action

It is a communicative marker, not a grammatical one.

Why は still feels like a subject marker

In many cases, the topic also happens to be the subject:

王子さまは こなやの娘を 愛している。

Here:

• 王子さま is the topic
• 王子さま is also the subject

Because the two coincide, は appears to mark the subject—even though it actually marks the topic.

Interaction with case particles

Discourse particles such as は and も can attach to case particles:

• に → には / にも
• で → では / でも
• と → とは / とも

…but not to が or を.

When は or も targets the same noun as が or を, it replaces them entirely.

So:

• が + は → は
• を + は → は

For example:

王子さまが こなやの娘を 愛している。
→ 王子さまは こなやの娘を 愛している。

The underlying subject marker が does not disappear—it is simply overridden by は, which has a higher communicative function.

This is why は seems to mark the subject.

Summary

The difference between は and が is difficult for English speakers because English often merges topic, subject, and familiarity into a single concept.

Key points:

• が is a case particle
  It marks grammatical roles such as the subject.
• は is a discourse particle
  It marks the topic—the starting point of the statement.
• Topic and subject are not the same
  Topic = what the sentence is about; subject = who performs the action.
• は can “override” が
  When subject and topic coincide, は replaces が.
• Discourse particles can combine with case particles—except が and を
• は does not mark what is objectively known
  It marks what the speaker assumes the listener can relate to.