In short

To say “A is B” in Japanese, name the topic, mark it with は (pronounced wa), then put the noun and です at the very end: 私は学生です。 (Watashi wa gakusei desu.) - I am a student. Japanese has no verb “to be” that changes for I / you / he - です is the same in every person, and the whole sentence swings between present and past, positive and negative, by changing that one word at the end.

The rule

The pattern is:

Noun (topic) + は + Noun + です

• 私は学生です。 (Watashi wa gakusei desu.) - I am a student. Topic 私 (watashi, “I”), marked by は, then the predicate noun 学生 (gakusei, “student”), then です.

Three things to notice immediately.

は is written は but said “wa”. When this kana does the job of marking the topic, it is pronounced wa, which is why the romaji in this course writes wa for it. Inside an ordinary word は is still ha (はな hana, “flower”). This spelling-vs-sound split is a permanent feature of Japanese, not a typo.

です never changes for person. English juggles am / are / is; Japanese does not. 私は学生です。田中さんは学生です。私たちは学生です。 - the ending is です in all of them. What you conjugate is tense and polarity, nothing else.

The predicate comes last. Everything else is setup; the sentence is not finished until です (or its negative/past form) lands. Train yourself to hold the ending until the end - this is the shape of every Japanese sentence you will ever build.

Building the four cells

Step 1 - Present positive: add です. 会社員です。 (Kaishain desu.) - (I) am an office worker.

Step 2 - Present negative: replace です with じゃないです or じゃありません. Do not attach ない straight to the noun - a noun is not an adjective and cannot be negated by itself. 会社員じゃないです。 / 会社員じゃありません。 (Kaishain ja nai desu. / Kaishain ja arimasen.) - (I) am not an office worker.

Step 3 - Past positive: replace です with でした. 会社員でした。 (Kaishain deshita.) - (I) was an office worker.

Step 4 - Past negative: put the past on the negative, not on です. 会社員じゃなかったです。 / 会社員じゃありませんでした。 (Kaishain ja nakatta desu. / Kaishain ja arimasen deshita.) - (I) was not an office worker. There is no ×じゃないでした.

The register ladder: では vs じゃ

じゃ is simply the spoken contraction of では (romanized de wa, because that は is the topic particle again). Both are polite; they differ in how formal they sound. ではありません belongs to writing, announcements and stiff business speech; じゃありません is the neutral polite standard; じゃないです is the same politeness but more conversational, and it is what you will hear most in everyday talk. Pick one and be consistent inside a sentence.

The plain counterpart だ

The plain (non-polite) form of です is だ (da): 学生だ (gakusei da). This course teaches the polite です／ます register first, so every example here ends in です. You will conjugate だ and its family when plain forms are taught properly - see Plain forms: dictionary, ない, た, なかった. Until then, keep to です.

Introducing yourself

The standard self-introduction stacks noun predicates and closes with a set greeting:

• はじめまして。 (Hajimemashite.) - How do you do.
• 私は+ name +です。 - I am …
• + country/city +から来ました。 (… kara kimashita.) - I come from … Treat 来ました as a fixed phrase for now; it is a verb form, and verbs arrive at Verb groups and the polite ます-form.
• どうぞよろしくお願いします。 (Dōzo yoroshiku onegai shimasu.) - Pleased to meet you. An untranslatable closing formula - learn it whole.

Dropping 私は. Once it is obvious you are talking about yourself, drop the topic. Repeating 私は in every sentence sounds like a robot insisting on who the subject is. 田中です。学生です。東京から来ました。 (Tanaka desu. Gakusei desu. Tōkyō kara kimashita.) - I’m Tanaka. I’m a student. I come from Tokyo. That is natural; the same three sentences each starting with 私は is not. Japanese omits anything the context already supplies.

も for “also”, and の for joining nouns (preview). も replaces は rather than joining it: 私も学生です。 (Watashi mo gakusei desu.) - I am a student too. Never ×私はも. And when one noun describes another, の joins them, modifier first and head last: 母の名前 (haha no namae) is my mother’s name, and a chain such as 姉の会社の名前 (ane no kaisha no namae), the name of my older sister’s company, narrows left to right onto its last noun. Full treatment of both at Particles へ, と, も, の, から, まで.

Forms & patterns

The four cells, with 学生 (gakusei, “student”) as the predicate noun:

The same four cells in the formal では variant:

The register ladder, most formal at the top:

です does not change for person:

One ending, four rows. English would need am / are / is / are.

Examples

Common mistakes

• 私わ学生です。 -> 私は学生です。 (Watashi wa gakusei desu.) - the topic particle is pronounced wa but written は. Writing わ here is the single most visible beginner error in Japanese.
• 私は学生ないです。 -> 私は学生じゃないです。 (Watashi wa gakusei ja nai desu.) - ない cannot attach directly to a noun. A noun predicate is negated with じゃ／では + ないです／ありません.
• 私は学生じゃないでした。 -> 私は学生じゃなかったです。 (Watashi wa gakusei ja nakatta desu.) - でした does not stack onto じゃない. Either put the past inside the negative (じゃなかったです) or use じゃありませんでした - never both patterns at once.
• 私は田中さんです。 -> 私は田中です。 (Watashi wa Tanaka desu.) - さん is an honorific for other people. Attaching it to your own name sounds self-important.
• 私はアメリカです。 -> 私はアメリカ人です。 (Watashi wa Amerikajin desu.) - A は B です means “A is B”, so this literally says “I am America”. Say the nationality (〜人) or use the set phrase アメリカから来ました.

Tips

• After a noun, です is the polite copula, and it carries the tense. It is what turns the bare noun 学生 into the statement “is a student”, and it is the only thing that moves when the sentence goes past or negative. Remember that this is specific to nouns: later, after an い-adjective (高いです), です adds politeness only, because 高い already predicates by itself - see い-adjectives and な-adjectives.
• Learn the four cells as a block, out loud: です - じゃないです - でした - じゃなかったです. Chant them with one noun (学生), then swap the noun. Almost every A1 sentence about identity, nationality, jobs, days and prices is one of these four, and か at the end turns any of them into a question with nothing else changing (会社員ですか。) - the next lesson’s subject.
• じゃ = では, contracted. If you can hear that じゃ is just では said fast, the whole family stops looking like four unrelated endings and becomes one pattern with a formality dial.
• Say less, not more. English demands an explicit subject in every clause; Japanese drops whatever is obvious. In a self-introduction, 私は belongs in the first sentence at most - after that, just 学生です。東京から来ました。