Monday, September 7, 2015

What is the difference between が and は?

What is the difference between が and は?

This question gets asked again and again, and what is worse, nobody seems to be able to come up with a simple, good answer.

これは本だ。(kore wa hon da) This is a book.
これが本だ。(kore ga hon da) This one is the book.

は is used to make a flat statement, without emphasis.
が is used to put emphasis in the preceding word.

それは何ですか? (sore wa nan desu ka) What is that?
これは本だ。(kore wa hon da) This is a book.

どれが本ですか?(dore ga hon desu ka)? Which one is the book?
これが本だ。(kore ga hon da) This one is the book.

They are not interchangeable, they have different meanings.
は and が often indicate the subject of the sentence, but not always.
That is probably the source of all confusion.
Maybe it is better to think that they have nothing to do with the subject.

は usually indicates the topic of the sentence.
The topic of the sentence is what the sentence is talking about, which is not necessarily the subject.
Let's see an example:

コーヒーは毎日飲んでいます。kōhī wa mainichi nonde imasu.
Speaking of coffee, I drink it every day.

When I say "コーヒーは", it means that I am going to talk about coffee.
As long as I don't change the topic, all subsequent sentences will all be about coffee. But coffee may not necessarily be the subject of the sentence.

Speaking of coffee,
I drink it every day
I love it,
I think it is delicious.

コーヒーは (kōhī wa)
毎日飲んでいますし、 (mainichi nonde imasu shi)
大好きだし、 (dai suki da shi)
とても美味しいと思います。 (totemo oshii to omoimasu)

Coffee is not the subject of the sentence. But all sentences after コーヒーは talk about coffee. Coffee is the topic of the sentences.
The subject is the pronoun "I" which can be omitted because it is obvious who the subject is.

Another example:

Speaking of Mr. Tanaka,
his house is tiny
but his dog is enormous.

田中さんは (Tanaka san wa)
家がとても小さいけど、 (uchi ga totemo chiisai kedo)
犬が凄く大きい。 (inu ga sugoku ookii)

Mr. Tanaka is neither the subject nor object of the sentences. But we are talking about his house and his dog, so he is the topic of the sentences.
The particle は has nothing to do with the subject or object of the sentence.

Both sentences below are acceptable:
田中さんの犬が大きい。(Tanaka san no inu ga ookii) Mr. Tanaka's dog is big.
田中さんは犬が大きい。 (Tanaka san wa inu ga ookii) Speaking of Mr. Tanaka, his dog is big.