「は」と「が」

The difference between ‘ha’ and ‘ga’ is one of the most difficult points for learners of Japanese.
Even if you use them incorrectly, the meaning will still be understood, so if you are communicating at a beginner level, don’t be afraid to make mistakes and communicate positively.
To reach the upper-intermediate level, you must understand these differences and be exposed to many examples.

In Japanese, both は (wa) and が (ga) are particles used to mark the subject of a sentence.
However, there is a difference in the way they are used.

The principles are as follows;

「は」：Indicates Topic and implies Contrast.
「が」：Mean Neutrality and Limitation

「は」：Topic and Contrast

The particle は (wa) is often used to contrast or compare different topics or to introduce a new topic in a conversation.

Topic Marking

は (wa) marks the topic of a sentence, which is the element that the sentence is about or the information the speaker wants to focus on.
The topic can be the subject of the sentence. (It can also be another element, such as an object or a location. )

(1) わたしはリンです
– I am Lin.

(2) ジョーはアメリカ人の先生です
– Joe is an American Teacher.

Here, は indicates the topic of the sentence.
It indicates that the conversation is about (1) Lin and (2) Joe.

Contrast

(3) 日本は夏だが、オーストラリアは冬だ
– It’s summer in Japan, but winter in Australia.

In this sentence, は in [日本は] indicates the topic.
On the other hand, [オーストラリアは] indicates a comparison or contrast (to Japan).

(4) 私は肉はきらいですが、魚はすきです。
– I don’t like meat, but I like fish.

The first [は] is for the topic, and the second one is for the contrast (to meat).

As for [contrast] usage, the two things being compared are not always mentioned clearly; see (5).

(5) （わたしは）ピザはきらいです
– I don’t like pizza.

Here, わたし[は] is for the topic (often omitted in Japanese).
In (5), the sentence does not compare “わたし” with “ピザ”.

This sentence compares pizza with something else, and implies that the person does not dislike the other food.

If you simply want to say you don’t like pizza, use “が ga”.

(6) （わたしは）ピザが嫌いです
– I don’t like pizza.

In (6), the implied contrast disappears, and it simply means that the speaker does not like pizza.

が：Neutrality and Limitation

が (ga), is used to mark the subject of a sentence, which is the element that performs the action in the sentence.

Neutrality

Unlike は (wa), が (ga) does not imply any contrast or comparison and it simply, neutrally identifies the subject of the sentence.

(7)雨がふってきた。
– It started to rain.

(8) 荷物が届いた。
– Package delivered.

Limitation

The other role of が is to limit the focus to the target object.

Here is an example to illustrate the difference:

(9) 私は学生です。
– “I am a student.”

Here, は marks わたし as the topic of the sentence, which is the information that the speaker wants to convey.

(10) 私が学生です。
– “I am a student.”

In (10), が (ga) marks 私 (watashi) as the subject of the sentence, which limits the focus target to わたし.
I am a student (and others are not).

が is often used in answer to a question, as it limits the focus; see (11)

(11) 果物で何が好きですか。　ぶどうが好きです。
– What is your favorite fruit?　I like grapes.

In this reply, you cannot use は.

Summary

「は」：Topic and Contrast
「が」：Neutrality and Limitation