The topic-comment sentence structure
Grammar: Core
Japanese speakers organize sentences around a topic and a comment. The topic tells the listener what the comment is about. は marks many topics, though context can leave one unstated. Because English grammar focuses on subjects and predicates, learners need to distinguish the topic from the grammatical subject.
Topics and Comments
English clauses contain a subject and a predicate. The subject names an actor or thing. The predicate states the action or describes the subject:
“The cat (subject) sleeps (predicate).”
In a topic-comment sentence, Japanese speakers use は to mark the topic and establish a frame of reference. The listener identifies that topic through prior conversation, shared knowledge, or context. The speaker puts information about it in the comment.
Examples
Consider a sentence with は:
| Japanese | Literal Translation | Natural English |
|---|---|---|
| 猫は寝ている。 | As for the cat, it is sleeping. | The cat is sleeping. |
The speaker uses は to mark 「猫」 (cat) as the topic. The listener can identify the cat from context. The comment 「寝ている」 (is sleeping) describes the cat.
The same sentence with が doesn’t mark a topic. It reads one of two ways, depending on context:
| Japanese | Context | Natural English |
|---|---|---|
| 猫が寝ている。 | Reporting what’s happening | Look, the cat’s sleeping. |
| 猫が寝ている。 | Answering “Who’s sleeping?” | It’s the cat that’s sleeping. |
With nothing set up beforehand, が presents the whole scene as new information, such as something the speaker has just noticed. When the question is who’s sleeping, が singles out the cat as the answer.
Topic and Subject
In many English sentences, one noun is both topic and subject. Japanese can assign those roles to different nouns.
| Role | Definition | Marked by | Function |
|---|---|---|---|
| Topic | What the conversation is about; the frame of reference | は is the common marker | Sets context for the comment |
| Subject | The actor or entity described by the predicate | が; は can replace が when the subject is also the topic | Fills a grammatical role in the clause |
Consider this sentence:
「象は鼻が長い。」
“As for elephants, the nose is long.” (“Elephants have long trunks.”)
- 象は (elephants) is the topic. It sets the frame: we’re talking about elephants in general.
- 鼻が (the nose/trunk) is the grammatical subject of the predicate 長い (is long).
- The speaker describes the trunk as long: elephants have long trunks.
Particles Used with Topics
| Particle | Primary Role | Nuance |
|---|---|---|
| は | Topic marker | Can mark contrast (e.g., 猫は… in contrast with the dog). Speakers use it for general statements. |
| が | Subject/case marker | Identifies the subject, presents new information, or marks the focus of a clause. |
| では, には, … | Topic marker after another particle | は can follow particles such as で, に, and と to make the whole phrase the topic: 日本では、… → “In Japan, …” |
Choosing は or が
- Speakers use は to say something about a topic in the conversation.
- Speakers use が to identify who or what performs an action, has a property, or enters the conversation as new information.
「誰が来ましたか？」 (Who came?)
「田中が来ました。」 “It’s Tanaka who came.”
The respondent uses が to identify the subject.
「田中は来ました。」 “Tanaka came, at least.”
Here Tanaka is the new information, so this は is contrastive: Tanaka came, which hints that others may not have.
How to Parse These Sentences
- Find the structure first. Identify any topic and its comment, then write natural English. A word-for-word translation often comes out awkward.
- Check は in context. It can mark the main topic or contrast one item with another.
- Recover omitted information. If the sentence omits its topic, ask what the speakers have discussed or can infer from the situation.
- Use literal glosses as study tools. Use “As for the cat, it is sleeping” to see the Japanese structure. Translate the sentence as “The cat is sleeping” in English.
- Practice in chunks. Read the sentence and label its [TOPIC] (if stated) and [COMMENT].