は versus が

The Core Difference

は（わ） marks the topic of the sentence — what the sentence is about. It sets the frame for the rest of the statement. が marks the subject — the doer of the action or the thing being described. In English, both often translate to the same word, but the nuance differs.

Consider:

• 私は学生です（わたしはがくせいです） — "I am a student." Here, は introduces "I" as the topic, and the sentence comments on it.
• 私が学生です（わたしががくせいです） — "I am the student." Here, が identifies "I" as the specific subject, often in answer to a question like "Who is the student?"

In the first, the focus is on the comment (being a student). In the second, the focus is on the subject (who is the student).

Where Both Work

In many sentences, both は and が are grammatically possible, but they shift the nuance.

• 象は鼻が長い（ぞうははながながい） — "Elephants have long trunks." Here, は marks the topic (elephants), and が marks the subject of the embedded description (noses). This is a classic example of the "double subject" construction.
• 彼は来る（かれはくる） — "He will come." This states a fact about him.
• 彼が来る（かれがくる） — "He will come." This emphasizes that it is he who will come, perhaps in contrast to someone else.

In general, は is used for general statements, known information, and contrasts. が is used for new information, specific identification, and when the subject is emphasized.

Cases Where Only が Is Possible

There are several situations where が is mandatory and は cannot be used.

1. With Certain Predicates

Some predicates require が to mark the subject. These include:

• 好き（すき） — to like: 私は猫が好きです（わたしはねこがすきです） — "I like cats."
• 嫌い（きらい） — to dislike: 彼は野菜が嫌いです（かれはやさいがきらいです） — "He dislikes vegetables."
• 上手（じょうず） — to be good at: 彼女はピアノが上手です（かのじょはピアノがじょうずです） — "She is good at the piano."
• 下手（へた） — to be poor at: 私は料理が下手です（わたしはりょうりがへたです） — "I am bad at cooking."
• 欲しい（ほしい） — to want: 子供が欲しいです（こどもがほしいです） — "I want children."
• できる — to be able to do: 日本語ができます（にほんごができます） — "I can speak Japanese."

In these, the particle が marks the object of the feeling or ability, and は cannot replace it. Note that the topic of the sentence can still be marked with は, as in the examples above.

2. In Relative Clauses

When a clause modifies a noun, the subject of that clause is marked with が, not は.

• 私が買った本（わたしがかったほん） — "the book I bought"
• 彼が作った料理（かれがつくったりょうり） — "the dish he made"

Using は in these relative clauses is ungrammatical.

3. In Questions with Interrogative Words

When the subject is an interrogative word (who, what, which), が is used.

• 誰が来ますか（だれがきますか） — "Who is coming?"
• 何が好きですか（なにがすきですか） — "What do you like?"

In the answers, が is also used to identify the specific person or thing.

• 田中さんが来ます（たなかさんがきます） — "Tanaka is coming."

4. In Negative Statements with は

Sometimes は is used to mark the subject in negative sentences to create a contrast or emphasis, but this is a separate use. For example:

• 私は行かない（わたしは いかない） — "I am not going." (neutral)
• 私が行かない（わたしがいかない） — "I am the one not going." (emphasizing)

However, in certain patterns like 〜は〜が, the が is required for the second part.

Common Misconception

Many learners think は and が are interchangeable, but they are not. The choice depends on the context and what you want to emphasize. A useful rule of thumb: は introduces the topic, が introduces the subject. When in doubt, consider whether you are making a general statement (は) or identifying a specific subject (が).

Practice

To master this, practice with sentences that use both particles. For example, describe your family:

• 私は兄が二人います（わたしはあにがふたりいます） — "I have two older brothers."

Here, は marks the topic (I), and が marks the subject of the existence (brothers).

Try creating sentences about likes, abilities, and experiences, always paying attention to which particle is required.

For more practice, see the grammar library and the particle game.