Wa vs Ga: Topic, Subject, Contrast, and Practice

Compare the sentences

The first answer identifies Tanaka as the missing person. In the second sentence, Tanaka is the topic and teacher is the description. は can also replace object を for contrast: お茶は飲みますが、コーヒーは飲みません. These are uses in stated contexts, not a rule that all new words always take が.

The basic difference

The second example can answer “Who is the teacher?” The first can answer “What does Tanaka do?” Both sentences can be grammatical; they organize the information differently.

Use the question to understand the answer

Talking about a person already under discussion

A: 田中さんは何をしていますか。 — What does Tanaka do?
B: 田中さんは日本語の先生です。 — Tanaka is a Japanese teacher.

Tanaka is the topic being discussed. The answer supplies information about him. In a natural conversation, B could also say 日本語の先生です without repeating the topic.

Identifying the person

A: だれが日本語の先生ですか。 — Who is the Japanese teacher?
B: 田中さんが日本語の先生です。 — Tanaka is the Japanese teacher.

The question asks for the identity of the subject. が is the normal beginner choice after だれ in this pattern, and the answer fills that same information slot.

Introducing something that is present

が often appears when you report a new observation or introduce a person or thing:

• 公園に犬がいます。 — There is a dog in the park.
• 机の上に本があります。 — There is a book on the desk.
• 雨が降っています。 — It is raining.

After introducing the dog, you can make it the topic:

公園に犬がいます。その犬は白いです。
There is a dog in the park. That dog is white.

This helps explain the common beginner shortcut “new information uses が; known information uses は.” It is a useful observation, not an absolute rule. A known person can still take が when the speaker is identifying or focusing on that person.

は can mark contrast

Consider this answer to a question about drinks:

コーヒーは飲みますが、お酒は飲みません。
I drink coffee, but I do not drink alcohol.

The two は phrases set up a contrast. は can replace the usual object particle を in a contrastive phrase; it does not simply mean “the subject.” Here the drinks are what the speaker drinks or does not drink.

Compare:

• コーヒーを飲みます。 — I drink coffee; a straightforward action sentence.
• コーヒーは飲みます。 — I do drink coffee; coffee is the topic or a contrast with something else.

The precise implication comes from the conversation. Do not assume that は always creates a strong contrast, or that it is only used for contrasts.

A sentence can contain both は and が

わたしは猫が好きです。
I like cats.

わたしは introduces the person whose preference we are discussing. 猫が identifies the thing liked in this common 好きです pattern. 好き behaves differently from an ordinary action verb such as 読みます; translating the English word “like” does not tell you to use を.

Another example is:

このレストランは料理がおいしいです。
The food at this restaurant is delicious.

このレストランは sets the broader topic; 料理が is the subject of おいしいです. A useful beginner sentence can therefore contain a topic and a more specific subject.

Avoid rules that are too broad

は and が have further uses in subordinate clauses and more advanced sentence patterns. The examples here focus on simple main clauses; they are not a replacement rule for every occurrence of は or が.

Use the distinction in a conversation

Before choosing a particle, write the question your answer should address. ‘Who is the teacher?’ asks for an identity; ‘What does Mina do?’ makes Mina the topic. A familiar person can still take が when identifying that person. Practise a full self-introduction and follow-up, then change the name and the question.

Practice in context

Choose the particle that best fits the stated context.

1. You are introducing your occupation: わたし（は・が）学生です。

2. Someone asks だれが来ますか (“Who is coming?”). You answer: 田中さん（は・が）来ます。

3. You notice a cat in a room and report it: 部屋に猫（は・が）います。

4. You contrast tea with coffee: お茶（は・が）飲みますが、コーヒー（は・が）飲みません。

5. Complete the common preference pattern: わたしは音楽（は・が）好きです。

6. You locate a bag already under discussion: かばん（は・が）机の下にあります。

7. You identify the book someone is asking for: これ（は・が）その本です。 The intended answer is ‘This is the one.’