This article is one in a series that comprehensively explains usage of は vs. が in Japanese. Most content is directly pulled from 『｢は｣ と ｢が｣』 by Hisashi Noda.
Which Part is the Topic?
This principle is also known as the principle of topic position. We use this to decide which part of the clause/sentence is the topic and where we should place it.
The topic is something that you want to talk about, and the comment is something you want to convey about the topic. So when choosing what becomes the topic and what becomes the comment, we can follow the general rule that the comment conveys one option among other options relating to the topic.
Choosing the Topic
Word-level Considerations
Many rules besides this general one are useful for choosing the topic and comment. First, we’ll take a look at one case that must become a comment.
| A noun will always be the comment if it is an: |
|---|
| Interrogative Word (e.g. 誰, どれ, どこ, 何) |
This is the reason why you’ll almost never see 誰, どれ, どこ, or 何 marked with は. If you do see an interrogative word with は, it’ll always be contrastive は, not topic-marking は, as is the case in (1).
1. だれは来て、だれは来なかったの？
Who came, and who didn’t?
Sentence-level Considerations
The next set of rules I’ll introduce aren’t hard-set, but general tendencies of topics in sentences. They can be summarized in the following table:
| Topic | Comment | |
|---|---|---|
| Noun Predicate | Words like 特徴 and 原因 | The details in question |
| Words like 高さ and 色 | The values in question | |
| "～というもの" | The explanation | |
| Adjective Predicate (Comparison) |
The adjective predicate | The noun subject |
| Adjective Predicate (No Comparison) |
The noun subject | The adjective predicate |
| Verb Predicate | The part that comes earlier in standard word order |
The rules for sentences with a noun predicate are somewhat self-explanatory according to our general rule. Words like 中心, 目的, 基盤, 限度, 値段, 年齢, 名前, and メニュー frequently become the topic, while their content becomes the comment.1 These are sentences like:
2. アジア人の食生活の特徴は、主食があることです。
What’s different about Asian diets is the abundance of staple foods.
3. 普通のコースターの所要時間は約3分ほどだ。
Each ride lasts about 3 minutes.
4. このナタデココは、ココナッツミルクを静かに寝かせて発行させたもの。
This nata de coco is made by fermenting coconut milk.
“～というものは” is commonly shortened to “～とは”.
5. 炭焼きとは、木材を熱分解して、揮発しやすい成分を可燃性のガスとして燃やしたり、蒸発にして追い出したりした後、炭素が燃えてしまう手前で燃焼を止める作業である。
Sumiyaki is the process of pyrolyzing raw lumber to remove its volatile components to the point just before carbon starts burning away.
For sentences with adjective predicates, we have two different rules. The first one covers adjective sentences that express some kind of comparison, which will often include phrases like “～のほうが (adjective)” and “～がいちばん (adjective)”. In this case, the adjective becomes the topic, and the noun subject is marked with exclusive が.
6. ｢でも、リカさんと一緒にいる永尾くんが、私の知ってる永尾くんの中で一番元気。｣
“Nagao always looks the happiest when I see him with Rika.”
7. ｢お茶にする、お酒にする？｣
｢お茶がいい｣
“Would you like tea or sake?”
“Tea, please.”
The second rule concerns adjective sentences that express no such comparison. These sentences will likely take the noun subject as its topic, marked by は.
8. 亭主関白の家は暗い。
Households with domineering husbands are depressing.
Sentences with verb predicates often have multiple case-marked nouns. The general rule with verb sentences is that whatever comes earliest in basic sentence order (subject-object-verb) becomes the topic. In (9), the subject (instead of the object) is the topic because it comes earlier in the SOV order.
9. その頃、三郎は刑務所の係長の部屋で茶坊主をしていた。
At that time, Saburou spent his days at the head of the jail’s room, tending to his every need.
The に case is typically expressed before the subject-marking が case in sentences with predicate ある (as in ～に～がある), so ～に is topicalized in (10).
10. ｢アンチ百恵｣としての聖子には、百恵的エロティシズムを歌わないという宿命がありました。
As the “anti-Momoe”, Seiko was destined to never sing with Momoe-esque eroticism.
Context-level Considerations
The concept of familiar information, as introduced in Topic Sentences, is also useful for determining the topic. Once again, this isn’t a hard-set rule, just a broad tendency topic sentences have.
Recall our definition for familiar information.
| Definition | Tends to Be... | |
|---|---|---|
| Familiar Information | - Anything present at the scene of the conversation. - Anything previously mentioned. - Anything related to something previously mentioned or present at the scene of the conversation. - Anything the speaker knows the listener is aware of. |
Topic |
As mentioned in the table, familiar information tends to become the topic. Consider the following examples.
11. 俺は中卒さ。
I’m a middle-school graduate, you see.
12. 途中に西宮名塩がある。同駅は複線電化時に名塩の各住宅団地のために作られた。
Nishinomiya-Najio is on the way there. The station of the same name was built when the line was electrified and double-tracked for the neighborhoods of Najio.
In (11), “俺” (I) is topicalized as familiar information because it refers to the speaker, who is by definition present at the scene of the conversation. It’s very common for first and second-person pronouns to be topicalized because the speaker and the listener are always going to exist in the context of the sentence.
In (12), “同駅” (the station of the same name) is topicalized because it is related to “西宮名塩” (Nishinomiya-Najio), a town which was mentioned in the previous sentence.
Some sentences violate this rule. In this next example, an inverted sentence, familiar information is marked by exclusive が, making it the comment.
13. しかし、天気は、大気の循環というか、気象全体がカオスになっているため、初期条件がほんの少し変わると、天候大異変になってしまう。これが天気予報の当たらない物理学的な理由である。
Weather isn’t a set cycle, but a chaotic system, where even the slightest alteration in starting conditions can cause massive changes in weather. This is why weather forecasts are sometimes off.
The reason why “これ” in (13) is marked with exclusive が is because the noun sentence rule we saw in Sentence-level Considerations took precedence over the familiar information rule. In fact, it is very common for inverted sentences to express familiar information as its comment.
Where is the Topic Placed?
In typical sentences with a topic, the topic is placed at the front of the sentence, and the comment is placed after it. Recall back to chapter 1 when we saw the topicalization of “この本” (this book) in the case structure “父がこの本を買ってくれた(こと)”.
14. この本は父が買ってくれた。
Likewise, we can topicalize the clause “この本を買ってくれた” (bought this book for me) in the case structure “父がこの本を買ってくれた(こと)”, and we’ll see that it’s also placed at the front.2
15. この本を買ってくれたのは父だ。
Inverting this sentence will then give us
16. 父がこの本を買ってくれたのだ。
which is the same structure as ｢君が主役だ。｣.
Thus, the usage of は/が changes depending on what part of the sentence the topic is in. If the topic is before the predicate, it is marked by は. If the topic is the predicate, the subject will be marked with exclusive が. Remember that sentences with the topic in the predicate are called inverted sentences.
Notice how (2) and (3) have approximately the same meaning. In many cases, a sentence and its inversion are interchangeable, but there are certain tendencies towards which version of the sentence is more likely to be expressed depending on context and what kinds of words are contained in it.
Not all sentences make sense when they’re inverted. Before we go over when to use inverted sentences, we should learn how to recognize which sentences can be inverted and which ones can’t.
How to Tell When Inversion is Possible
To find out when it’s possible to invert a sentence, we need to look at the meaning of its topic and comment. In topic sentences, the topic is either referential or predicative. If the topic is referential, the comment is predicative; and if the comment is referential, then the topic is predicative.
| Definition | If Topicalized | |
|---|---|---|
| Referential | Some individual object/concept | Sentence cannot be inverted |
| Predicative | Some aspect/category of the referential element |
Sentence can be inverted |
Let’s look at a sentence that can’t be inverted. Consider sentence (17) and its inversion (18).
17. ビルの高さは85mです。
The building is 85 meters tall.
18. ×85mがビルの高さです。
The topic in (17) and (18) is “ビルの高さ” (the height of the building), and the comment is “85m” (85 meters). “ビルの高さ” refers to the concept of the building’s height, which is referential in this sentence. “85m” describes the value of the building’s height, making it the predicative element of this sentence. In fact, nouns that express some kind of quantity are almost always predicative. As you can see in the table, sentences where the referential element is topicalized cannot be inverted, which is why (18) sounds awkward.
Now let’s go back to our classic example ｢君が主役だ。｣. In this sentence, “君” (you) is the referential element, and “主役” (lead actor) is the predicative element. Since the predicative element is the topic, this sentence can be inverted.
19. 主役は君だ。
20. 君が主役だ。
You’re the lead actor.
If, however, we topicalize the referential element “君”, it is no longer possible to invert the sentence.
21. 君は主役だ。
You’re a lead actor.
22. ×主役が君だ。
In the example ｢その火事の原因は漏電だ。｣, the referential element is “漏電” (electrical fault) and the predicative element is “その火事の原因” (the cause of the fire). We can invert this sentence because the predicative element is topicalized.
23. その火事の原因は漏電だ。
24. 漏電がその火事の原因だ。
The cause of the fire was an electrical fault.
It makes little sense to topicalize the referential element here, so neither (25) nor (26) are natural.
25. ×漏電はその火事の原因だ。
26. ×その火事の原因が漏電だ。
Adjectives and verbs are always predicative in this system. In other words, it’s almost always possible to invert a sentence when an adjective or verb is the topic.
27. いちばんいいのはダイヤだ。
28. ダイヤがいちばんいい。
Diamonds are the best.
When to Use Inverted Sentences
When it comes to inversion, there are three types of sentences:
- Sentences that can't be inverted sentences
- Sentences that are sometimes inverted sentences
- Sentences that are often inverted sentences
We just learned how to identify sentences that can’t be inverted (a). Now, let’s go over sentences in type (b) and (c).
| Sometimes Inverted Sentences | Often Inverted Sentences |
|---|---|
| - Sentences with a noun topic - Sentences with a verb topic (nominalized or not) - Sentences in which the comments are the details of topics like 特徴 or 原因 |
- Sentences with an adjective topic (nominalized or not) - Sentences in which the comment is familiar information - Sentences in which the comment is an interrogative word |
Example (23) falls into type (b) (sometimes inverted sentences) because it has a noun topic, and its comment expresses the details of the topic “原因”. You are more likely to see ｢その火事の原因は漏電だ。｣ than its inversion ｢漏電がその火事の原因だ。｣.
(29) also falls into type (b), because it has a verb topic (nominalized). You are more likely to see ｢そう言ったのは山田だ。｣ than its inversion ｢山田がそう言ったのだ。｣.
29. そう言ったのは山田だ。
Yamada said that.
In (30), the second sentence is type (c).
30. ｢バリバリしゃぶりついてるじゃないの、いつもは。｣
｢そう、しゃぶりつくのが、本当は一番おいしいんだよ。｣
“Why do you always suck on it like that?”
“It tastes better when you suck on it.”
Although its topic is a nominalized adjective, the sentence is expressed as an inverted sentence because its topic is nonetheless derived from an adjective. The last example in the previous section, (27), is also more commonly expressed as an inverted sentence because its topic is an adjective.
Sometimes, you’ll have conflicting principles in the same sentence.
31. これがそばの実です。
This is buckwheat grain.
In (31), the topic is a noun, but the comment “これ” refers to familiar information.3 In this case, the rule about familiar information is taking precedence, making it an inverted sentence of type (c). The uninverted ｢そばの実はこれです。｣ is also possible, but less common.
32. 結局どちらが勝ったんですか？
So, who won in the end?
(32) has a nominalized verb predicate, but it also has an interrogative word as its comment. Here, the rule about interrogative words is taking precedence, making it an inverted sentence of type (c). The uninverted ｢結局勝ったのはどちらですか？｣ is also possible, but less common.
Continued in 7. Other Usages and More は Structures…
Notes
-
These sentences fit into the ｢かき料理は広島が本場だ。｣ structure. ↩
-
This sentence fits into the ｢花が咲くのは7月ごろだ。｣ structure. ↩
-
This sentence violates the principle of topicalizing familiar information, like the example (16) in Choosing the Topic: Context-level Considerations ↩