Japanese marks the job a word is doing with a small word placed after it, called a particle. Two particles, は and が, both sit roughly where an English subject would sit, and choosing between them is the longest-running puzzle in the language. The good news is that a handful of rules of thumb will carry you through almost every sentence you can currently build, and that the rest of the understanding arrives slowly, on its own, from listening.
は marks the topic
は is written with the hiragana は, but as a particle it is always pronounced wa. It marks the topic: the thing the rest of the sentence is about. A clumsy but honest English gloss is "as for".
わたし は がくせい です
watashi wa gakusei desu
As for me, I am a student
やまださん は せんせい です
yamada san wa sensei desu
Mr Yamada is a teacher
これ は ほん です
kore wa hon desu
This is a book
The shape is always the same. You announce what you are going to talk about, then you say something about it. The topic is normally something the listener already has in mind: yourself, the person in front of you, the object you are pointing at.
Once a topic is set, it stays set. That is why Japanese leaves so much out. After わたし は がくせい です, the next sentence can simply be にほんじん です, and everyone knows you are still talking about yourself. Nothing needs repeating until the subject of conversation changes.
が marks the subject
が marks the subject in the narrow grammatical sense: the thing that is, or does, whatever comes next. Where は steps back and frames, が points.
わたし が やまだ です
watashi ga yamada desu
I am Yamada (I am the one you are looking for)
たなかさん が せんせい です
tanaka san ga sensei desu
Tanaka is the teacher (he is the one)
こちら が わたし の うち です
kochira ga watashi no uchi desu
This is my house (here it is)
Read those English translations again and notice that each one carries a small extra weight. が does not just say who; it selects one out of several. English does the same work with stress of voice: "I am Yamada". Japanese does it with a particle instead, which is why Japanese sentences can be spoken flatly and still be precise.
Old information and new information
The most useful single rule of thumb is this: は introduces what the listener already has in mind, and が supplies what they do not.
Put the same two words either side of the two particles and the difference is easy to hear.
やまださん は せんせい です
yamada san wa sensei desu
Yamada is a teacher (here is something about Yamada)
やまださん が せんせい です
yamada san ga sensei desu
Yamada is the teacher (Yamada is the one who is)
In the first, everyone already knows who Yamada is and you are adding a fact. In the second, everyone already knows there is a teacher and you are identifying which person it is. The new part of the sentence is whichever side of the particle the listener did not have.
This is also why question words take が, which you will see in a later lesson. A question word is new information by definition, so it can never be a topic.
は also draws contrast
The second job of は is contrast. Because は lifts something out and holds it up, it often carries a quiet "at least this one" with it.
きょう は やすみ です
kyou wa yasumi desu
Today is a day off (whatever the other days are)
これ は ほん です。それ は ざっし です
kore wa hon desu. sore wa zasshi desu
This is a book. That one is a magazine
あした は しけん です
ashita wa shiken desu
Tomorrow is the exam (as opposed to any other day)
Two は in a row, as in the middle example, is the standard way to set two things against each other. Japanese speakers use this constantly, and it is a large part of why は turns up more often than が in ordinary conversation.
The topic is not always the subject
Here is where the "as for" gloss earns its keep. は never claims that the thing before it is the subject. It claims only that the sentence is about it. That licence produces the most famous sentence in beginner Japanese.
わたし は コーヒー です
watashi wa koohii desu
I will have the coffee
Nobody hears that as a claim that you are made of coffee, because は did not say you were the subject. It said the sentence concerns you, and the sentence goes on to be about coffee. Swap in が and the joke becomes real: わたし が コーヒー です would pick you out of a line-up of drinks.
あした は しけん です
ashita wa shiken desu
Tomorrow, there is an exam
わたし は あした です
watashi wa ashita desu
Mine is tomorrow (in a conversation about appointments)
What learners get wrong
Learners who memorised "が marks the subject" put が on every "I". It is grammatical, but it sounds as though you are permanently correcting somebody about who you are. Use は unless you have a reason not to.
The second common error is reading the particle は as ha. In a word it is ha, as in はち. As a particle it is wa, always, with no exceptions to worry about.
The third is treating は as though it meant "is". It does not mean anything in English. です does the "is" work; は only marks what the sentence is about.
Rules of thumb worth memorising
- Talking about yourself, or about anything already in play: は.
- Naming which one out of several: が.
- Setting two things against each other: は.
- Genuinely unsure at this stage: は is the safer default, and the error it produces is milder.
The honest part
Those rules will not cover everything, and you should know that now rather than discovering it in a year. は and が interact with grammar you have not met yet: adjectives of feeling, verbs of ability, clauses inside clauses, and the verbs for existence. In some of those, the choice flips. Native speakers make the right choice without being able to explain it, and whole books have been written trying.
Do not wait to understand the pair before you speak. Use は as your default, produce sentences, and when you hear が in a film or a conversation, stop for a second and ask yourself what it was picking out. Understanding here arrives by accumulation, not by rule.
Vocabulary
- わたし (watashi): I, me
- やまださん (yamada san): Mr or Ms Yamada
- たなかさん (tanaka san): Mr or Ms Tanaka
- がくせい (gakusei): student
- せんせい (sensei): teacher
- にほんじん (nihonjin): a Japanese person
- ほん (hon): book
- ざっし (zasshi): magazine
- コーヒー (koohii): coffee
- うち (uchi): house, home
- きょう (kyou): today
- あした (ashita): tomorrow
- やすみ (yasumi): day off, holiday
- しけん (shiken): exam
- こちら (kochira): this one here, this way (polite)