What's the difference between wa (は) and ga (が)?


When is it correct to use は but not が, and when is it correct to use が but not
は? Are there any times when you can use either without changing the meaning of
the sentence? How does switching change the meaning of a sentence?




は and が are a bit complex because they have several meanings, and some of the
shades of meaning of wa and ga are a bit hard to distinguish casually.

The best coverage of this that I have read is ["The Structure of the Japanese
Language"](https://rads.stackoverflow.com/amzn/click/com/0262110490) by Susumu
Kuno (written in English). I'm going to attempt to synthesize some of that
here, but Kuno's explanation is much more complete. I wrote most of this as an
answer to a similar question on an internet forum about a year ago, so if you
find it there, that's me too.

There are two meanings to は, and three for が. は is used for contrast and
thematic reference. が is used as a direct object marker for certain
verbs/verbals, an exhaustive subject marker, and as a 'neutral-descriptive'.

は is often called the 'topic marker', in contrast to the 'subject marker' of
が, but the key difference is context. Imagine, if you will, a big box of
things that have been mentioned in a conversation. We'll call this box the
"universe of discourse". Certain constructions can only be used with things
that are in this "universe". This sounds ridiculously abstract, until you
realize that we do this in English as well.

**English Anaphoric Phrases** :

> The boy was bouncing a ball off the store wall.

is not a valid sentence in isolation.

Now, several of you are freaking out right now, since that seems like a
perfectly reasonable English phrase. It is... but not without context. If I
start the conversation with that phrase, I've left out enough important
details that you'd be reasonable to suspect I was playing a game of quotations
(or insane...).

> I saw a boy in Wallgreen's last night. The boy was bouncing a ball off the
> store wall.

provides the needed context. The first sentence introduces a boy into the
context of the conversation, the "universe of discourse", and "The" selects
him out of it as the particular object I wish to make a statement on.

> A boy was bouncing a ball off the store wall in Wallgreen's.

is perfectly reasonable. From this we can see that we use "A" to introduce
elements to our "universe of discourse", and "the" to select them out. There
are several things that are considered to be always in this universe, such as
personal referents. Note my first example is perfectly fine if your listener
is aware you have a son. This can get a bit messy in English, so let's head to
Japanese before the analogy fails.

**Thematic wa**

In Japanese, the thematic は is used with generic noun phrases ("the brits") or
things that are already in the universe of discourse. It's sometimes tricky to
nail down exactly what is there, but the general idea is that you don't
introduce things to the conversation using thematic は。 This is why you cannot
use question words with は, the non-specified referent cannot be in the
universe of discourse. (だれは来ましたか?) <\--- BAD! INVALID! DO NOT USE!

**Contrastive wa**

Contrastive は, on the other hand, is much more free, and this partly explains
why 「雨は降っていますが、たいしたことはありません」 is valid, while 「雨は降っています。」 is not.** Note that
this is more complicated than the textbook contrastive は, as the contrast
extends through the meaning of the final predicate, not just the things before
the は marker.

And unfortunately it can be ambiguous which は you're looking at. Kuno's
example is 「わたくしが知っている人はパーティーに来ませんでした」. If read as thematic は (if you were
talking about all the people you know... such as all your new Japanese
friends), it means "Speaking of the people I know, they did not come to the
party". If you read it as contrastive, it means "People came to the party, but
none that I know."

There can be only one thematic は in a sentence. If you see a second one, the
second is certainly contrastive, and the first might be.

**On to が...** The first meaning of が is trivial, the direct object of certain
verbs, particularly those having to do with personal capability or preference,
replacing the normal direct object particle を, e.g.「だれが映画が好きですか？」. This is
adequately covered elsewhere, and aside from the curious subset of verbs on
which this is used, is mostly uninteresting.

**Exhaustive listing ga vs neutral description ga**

The other two meanings, exhaustive-listing and neutral description, are a bit
tricky to understand. Any が can be an exhaustive-listing が, but neutral
description only works with action verbs, existential verbs, and
adjectives/nominal adjectives that represent state change. "Sentences of
neutral description present an objectively observable action, existence, or
temporary state as a new event." Neutral description is a valid way of
introducing something to the universe of discourse, but it is far from the
only one.

**For predicates with stative verbs or adjectives/nominal-adjectives of
permanent states, が can only be interpreted as exhaustive-listing.**
Exhaustive-listing works similar to contrastive は, implying contrast to the
rest of the universe of discourse.

> A:「だれが日本語を知っていますか？」 B:「ジョンが日本語できます」

できる is a non-action verb, so this is exhaustive-listing. Assume that we are
talking about the three new students: Jon, Bill and Tom. If B knows that Jon
and Tom can both speak Japanese, B just lied. If B knows Jon can speak
Japanese, but doesn't know about the others, the contrastive は is appropriate
to use instead of が.

Note that this is only a quick overview of the whole topic, and each of these
uses has special-cases that bends the rules... but this is a decent summary of
the common cases.

** It's very hard to think of a valid way to introduce rain (in a non-general
way) to the conversation without it falling. I'm sure someone can dream up a
way for it to work, but for the general meaning of "it's raining", は is not
correct.




は and が are a bit complex because they have several meanings, and some of the
shades of meaning of wa and ga are a bit hard to distinguish casually.

The best coverage of this that I have read is ["The Structure of the Japanese
Language"](https://rads.stackoverflow.com/amzn/click/com/0262110490) by Susumu
Kuno (written in English). I'm going to attempt to synthesize some of that
here, but Kuno's explanation is much more complete. I wrote most of this as an
answer to a similar question on an internet forum about a year ago, so if you
find it there, that's me too.

There are two meanings to は, and three for が. は is used for contrast and
thematic reference. が is used as a direct object marker for certain
verbs/verbals, an exhaustive subject marker, and as a 'neutral-descriptive'.

は is often called the 'topic marker', in contrast to the 'subject marker' of
が, but the key difference is context. Imagine, if you will, a big box of
things that have been mentioned in a conversation. We'll call this box the
"universe of discourse". Certain constructions can only be used with things
that are in this "universe". This sounds ridiculously abstract, until you
realize that we do this in English as well.

**English Anaphoric Phrases** :

> The boy was bouncing a ball off the store wall.

is not a valid sentence in isolation.

Now, several of you are freaking out right now, since that seems like a
perfectly reasonable English phrase. It is... but not without context. If I
start the conversation with that phrase, I've left out enough important
details that you'd be reasonable to suspect I was playing a game of quotations
(or insane...).

> I saw a boy in Wallgreen's last night. The boy was bouncing a ball off the
> store wall.

provides the needed context. The first sentence introduces a boy into the
context of the conversation, the "universe of discourse", and "The" selects
him out of it as the particular object I wish to make a statement on.

> A boy was bouncing a ball off the store wall in Wallgreen's.

is perfectly reasonable. From this we can see that we use "A" to introduce
elements to our "universe of discourse", and "the" to select them out. There
are several things that are considered to be always in this universe, such as
personal referents. Note my first example is perfectly fine if your listener
is aware you have a son. This can get a bit messy in English, so let's head to
Japanese before the analogy fails.

**Thematic wa**

In Japanese, the thematic は is used with generic noun phrases ("the brits") or
things that are already in the universe of discourse. It's sometimes tricky to
nail down exactly what is there, but the general idea is that you don't
introduce things to the conversation using thematic は。 This is why you cannot
use question words with は, the non-specified referent cannot be in the
universe of discourse. (だれは来ましたか?) <\--- BAD! INVALID! DO NOT USE!

**Contrastive wa**

Contrastive は, on the other hand, is much more free, and this partly explains
why 「雨は降っていますが、たいしたことはありません」 is valid, while 「雨は降っています。」 is not.** Note that
this is more complicated than the textbook contrastive は, as the contrast
extends through the meaning of the final predicate, not just the things before
the は marker.

And unfortunately it can be ambiguous which は you're looking at. Kuno's
example is 「わたくしが知っている人はパーティーに来ませんでした」. If read as thematic は (if you were
talking about all the people you know... such as all your new Japanese
friends), it means "Speaking of the people I know, they did not come to the
party". If you read it as contrastive, it means "People came to the party, but
none that I know."

There can be only one thematic は in a sentence. If you see a second one, the
second is certainly contrastive, and the first might be.

**On to が...** The first meaning of が is trivial, the direct object of certain
verbs, particularly those having to do with personal capability or preference,
replacing the normal direct object particle を, e.g.「だれが映画が好きですか？」. This is
adequately covered elsewhere, and aside from the curious subset of verbs on
which this is used, is mostly uninteresting.

**Exhaustive listing ga vs neutral description ga**

The other two meanings, exhaustive-listing and neutral description, are a bit
tricky to understand. Any が can be an exhaustive-listing が, but neutral
description only works with action verbs, existential verbs, and
adjectives/nominal adjectives that represent state change. "Sentences of
neutral description present an objectively observable action, existence, or
temporary state as a new event." Neutral description is a valid way of
introducing something to the universe of discourse, but it is far from the
only one.

**For predicates with stative verbs or adjectives/nominal-adjectives of
permanent states, が can only be interpreted as exhaustive-listing.**
Exhaustive-listing works similar to contrastive は, implying contrast to the
rest of the universe of discourse.

> A:「だれが日本語を知っていますか？」 B:「ジョンが日本語できます」

できる is a non-action verb, so this is exhaustive-listing. Assume that we are
talking about the three new students: Jon, Bill and Tom. If B knows that Jon
and Tom can both speak Japanese, B just lied. If B knows Jon can speak
Japanese, but doesn't know about the others, the contrastive は is appropriate
to use instead of が.

Note that this is only a quick overview of the whole topic, and each of these
uses has special-cases that bends the rules... but this is a decent summary of
the common cases.

** It's very hard to think of a valid way to introduce rain (in a non-general
way) to the conversation without it falling. I'm sure someone can dream up a
way for it to work, but for the general meaning of "it's raining", は is not
correct.

